From nobody Wed Nov 27 06:37:06 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5A6F01C2DA1; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; cv=none; b=kg8ApVqc6e4MpglpTSGTV9vxPePeNs7WwNa1p6RUyTihEUG+xpkLQy6X93jyDHZRyGdq6K4BDLiIr1ITwMqDip75U5JqdxBpYHy9UBPSQwnmUKDsu3MZGKmq2c/xfcNb2atKi5QxTzlaM1CCDzp9CE04e6zD+i4U8teINAnyYBA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; c=relaxed/simple; bh=YtrJn4vc+Mgz9wgw7+EugcgaEZCddJzBtXAuSeGGRxU=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Td8mp8kWVmIWcuY1tuabB1oDG/KJJG5+/o4p3GT1hrvAv40MBXQPwBXGl96jfg+ZQ+DRcPKiHn0Av87mOoAwNVdoHnPrDIQKrSXoMHujhEXTS5S/N83enAhpKfSpVm+VVfehfO64yeILgmeZ49unCFrpdgKy7A15/x9qmElE57U= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=T/DvKyih; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="T/DvKyih" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E52A1C4CEC3; Fri, 11 Oct 2024 17:39:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728668373; bh=YtrJn4vc+Mgz9wgw7+EugcgaEZCddJzBtXAuSeGGRxU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=T/DvKyihzpbz0F1UjqpYZmPGTveIK/9TCnBiQ5W3BJVe3uTau+kajEEG2W7tkfJHZ h1LaE1XUR1dgbsZfPI+CJv7Ax+r5wvBW1ekLSIQ/XO4NbEBlMSoYaccUf1w1h9YMON u2luxl/PZYPUQLTTDaPkIgWJAaLiRRVnDLQS8o3LLOh+BBaDUceRhJA8a90jLoexuy j/MCaX9f5ZglIJnnavL3Qml//0rTZ61f5UK7e3E7DXyI+sE8lYzwVnrG9+aNhPHhqX WzchLutmfhOlCMg5t54ZA0poLy0UjxtqMdOCeQCiYei1zN1cFSpShi0j1oBjnKvAcf LtT/wZIt7QeUg== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 986CACE0BB1; Fri, 11 Oct 2024 10:39:32 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH v2 rcu 01/13] srcu: Rename srcu_might_be_idle() to srcu_should_expedite() Date: Fri, 11 Oct 2024 10:39:19 -0700 Message-Id: <20241011173931.2050422-1-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> References: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" SRCU auto-expedites grace periods that follow a sufficiently long idle period, and the srcu_might_be_idle() function is used to make this decision. However, the upcoming light-weight SRCU readers will not do auto-expediting because doing so would cause the grace-period machinery to invoke synchronize_rcu_expedited() twice, with IPIs all around. However, software-engineering considerations force this determination to remain in srcu_might_be_idle(). This commit therefore changes the name of srcu_might_be_idle() to srcu_should_expedite(), thus moving from what it currently does to why it does it, this latter being more future-proof. Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- kernel/rcu/srcutree.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 31706e3293bce..9ff4ded609ba5 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -1139,7 +1139,8 @@ static void srcu_flip(struct srcu_struct *ssp) } =20 /* - * If SRCU is likely idle, return true, otherwise return false. + * If SRCU is likely idle, in other words, the next SRCU grace period + * should be expedited, return true, otherwise return false. * * Note that it is OK for several current from-idle requests for a new * grace period from idle to specify expediting because they will all end @@ -1159,7 +1160,7 @@ static void srcu_flip(struct srcu_struct *ssp) * negligible when amortized over that time period, and the extra latency * of a needlessly non-expedited grace period is similarly negligible. */ -static bool srcu_might_be_idle(struct srcu_struct *ssp) +static bool srcu_should_expedite(struct srcu_struct *ssp) { unsigned long curseq; unsigned long flags; @@ -1469,14 +1470,15 @@ EXPORT_SYMBOL_GPL(synchronize_srcu_expedited); * Implementation of these memory-ordering guarantees is similar to * that of synchronize_rcu(). * - * If SRCU is likely idle, expedite the first request. This semantic - * was provided by Classic SRCU, and is relied upon by its users, so TREE - * SRCU must also provide it. Note that detecting idleness is heuristic - * and subject to both false positives and negatives. + * If SRCU is likely idle as determined by srcu_should_expedite(), + * expedite the first request. This semantic was provided by Classic SRCU, + * and is relied upon by its users, so TREE SRCU must also provide it. + * Note that detecting idleness is heuristic and subject to both false + * positives and negatives. */ void synchronize_srcu(struct srcu_struct *ssp) { - if (srcu_might_be_idle(ssp) || rcu_gp_is_expedited()) + if (srcu_should_expedite(ssp) || rcu_gp_is_expedited()) synchronize_srcu_expedited(ssp); else __synchronize_srcu(ssp, true); --=20 2.40.1 From nobody Wed Nov 27 06:37:06 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5A5D61BE86E; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; cv=none; b=VE7sbfkFiZXatFItYEYDTHBvHf2A6rbrxpwpKTCsPWG/e1oSH2daQhV6T6zxWcfxdOvIBG4FcJK+930B+KycSVs4pKv2rCFRcpHOum3drvp3QYuroFqaKSy0WLqggD0gVRQp8/vQB3s1np/yWwee2Yy2TtDgt7GEdhV9j1gLZUk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; c=relaxed/simple; bh=wmL8nD35K+D183HPbTxmWpox+7fCqVw7eRDQh/aakYc=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=CjoP/cqx4o8EzUiXXPfc6oluqWs4MDLTDPwRUTzDI7BNUw+eGnjy3s+ASYOWaPS0TYBDcKHxhooG2h013HVzU9JwuL9GhFcs/byCbxMydvjzaKoN2NBuMr5vIoeatxeR50w3jFQZ4qn6RRdmYhAAjHQsVmj8wHKjN517D0vE0cc= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=CnyJ0mPn; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="CnyJ0mPn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 01CE3C4CECE; Fri, 11 Oct 2024 17:39:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728668373; bh=wmL8nD35K+D183HPbTxmWpox+7fCqVw7eRDQh/aakYc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CnyJ0mPn2Mju9oCnyXhNKnku/qSFeWAAZ6DUyXDP0ok1IcZsp2GZrj7eR6/Gq32Sc 9rlDtu66GRN/b4PC31YGdIuOK1bp7mKJlxlRyWBlL77A5T312HTNK3mDgbVTit4WZo RBKnW7vJkrT+y0cd/fYsPLddZjLN9ZksJOhmFmKtYSTdfXKapP40q3REtQTtnVOazn MpEu4vZ3G9xnmhfsn4bFJlVTBezcpggpyRzNCEHzYUp9cgIGCggNrQLW2Agadt8xWa Tf4/AfEVolX/7k0gRmZ2B3qw73nD+sW8egkB0Jl3PZM3cMfWfX0+9FSoqg0YU+d2QW TEi51Dk/1bN6A== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 9C27DCE0BB3; Fri, 11 Oct 2024 10:39:32 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH v2 rcu 02/13] srcu: Introduce srcu_gp_is_expedited() helper function Date: Fri, 11 Oct 2024 10:39:20 -0700 Message-Id: <20241011173931.2050422-2-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> References: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Even though the open-coded expressions usually fit on one line, this commit replaces them with a call to a new srcu_gp_is_expedited() helper function in order to improve readability. Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- kernel/rcu/srcutree.c | 14 ++++++++++++-- 1 file changed, 12 insertions(+), 2 deletions(-) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 9ff4ded609ba5..e29c6cbffbcb0 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -418,6 +418,16 @@ static void check_init_srcu_struct(struct srcu_struct = *ssp) spin_unlock_irqrestore_rcu_node(ssp->srcu_sup, flags); } =20 +/* + * Is the current or any upcoming grace period to be expedited? + */ +static bool srcu_gp_is_expedited(struct srcu_struct *ssp) +{ + struct srcu_usage *sup =3D ssp->srcu_sup; + + return ULONG_CMP_LT(READ_ONCE(sup->srcu_gp_seq), READ_ONCE(sup->srcu_gp_s= eq_needed_exp)); +} + /* * Returns approximate total of the readers' ->srcu_lock_count[] values * for the rank of per-CPU counters specified by idx. @@ -622,7 +632,7 @@ static unsigned long srcu_get_delay(struct srcu_struct = *ssp) unsigned long jbase =3D SRCU_INTERVAL; struct srcu_usage *sup =3D ssp->srcu_sup; =20 - if (ULONG_CMP_LT(READ_ONCE(sup->srcu_gp_seq), READ_ONCE(sup->srcu_gp_seq_= needed_exp))) + if (srcu_gp_is_expedited(ssp)) jbase =3D 0; if (rcu_seq_state(READ_ONCE(sup->srcu_gp_seq))) { j =3D jiffies - 1; @@ -867,7 +877,7 @@ static void srcu_gp_end(struct srcu_struct *ssp) spin_lock_irq_rcu_node(sup); idx =3D rcu_seq_state(sup->srcu_gp_seq); WARN_ON_ONCE(idx !=3D SRCU_STATE_SCAN2); - if (ULONG_CMP_LT(READ_ONCE(sup->srcu_gp_seq), READ_ONCE(sup->srcu_gp_seq_= needed_exp))) + if (srcu_gp_is_expedited(ssp)) cbdelay =3D 0; =20 WRITE_ONCE(sup->srcu_last_gp_end, ktime_get_mono_fast_ns()); --=20 2.40.1 From nobody Wed Nov 27 06:37:06 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5A6A01C245D; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; cv=none; b=kA7ROzqjYOJIwCqw03PSHvH6bh6leC7B0HE1uHUZm3FlpEcVzvQPtj7sgPBV5E5M1xME6WUDLNJmmOlrJqETZ9tVG9GVOGaI5NEWra3QmgwXYQEdVRvL2JSSRltH8NIdRDqMT1rgDR3dM7U8Bp3kZSS8LJZv2GPb+PAR893CY0I= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; c=relaxed/simple; bh=Zx5VaivUvDu8VT1tnLqC/VtTV/C14Gn+/PcOHscidtA=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=uwcaxZVbs+EjRuezOTPaQCYH9na39FpP3p6wgrF5Ig8SEov0q1ZtW/E9VaF8tnxrM53y/VjQAzPzWLVvTKt6s6OxRwJfnFfvNNbNzZOEk9kM2av+/YuVY/gxjhHDHpWYjQMqJeQYKtCdBxmYPpqvL/RLN093nQHIDgfu32CGGts= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=TG2opX/X; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="TG2opX/X" Received: by smtp.kernel.org (Postfix) with ESMTPSA id F3F19C4CEC7; Fri, 11 Oct 2024 17:39:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728668373; bh=Zx5VaivUvDu8VT1tnLqC/VtTV/C14Gn+/PcOHscidtA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TG2opX/XLPsByEmZEtpcSI6VXOnugeq+tw7QHW71QoyUKf0NSaBoSu3S0nEd50XHt 4K8hYX7N80lJ5sdqfW6O0eop4DhhpBMOCNrI+IM0efWZ38KtBwWK52WEZ2a4eDZxF2 ABEsZHkcPfcm3UE84Jm1egVKt13yVroeozNZZrJr/UaCGgR0XJcaGpFYYI/6aFspY+ lzlUdO5KGwTT1ab5wwlhkwRMhNHqCHcWXRGKofdugFc3FKJ5Yb6AxRj7WTaV/FGZpJ YRZhEP4HqwFHna0exP6a3boKlaYIBufgQB1PMc/WmZRVx5fd2Q0SpO0pmnIaneD/+i PEY0mFt+aq6bw== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 9F30BCE0EA5; Fri, 11 Oct 2024 10:39:32 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH v2 rcu 03/13] srcu: Renaming in preparation for additional reader flavor Date: Fri, 11 Oct 2024 10:39:21 -0700 Message-Id: <20241011173931.2050422-3-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> References: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Currently, there are only two flavors of readers, normal and NMI-safe. A number of fields, functions, and types reflect this restriction. This renaming-only commit prepares for the addition of light-weight (as in memory-barrier-free) readers. OK, OK, there is also a drive-by white-space fixeup! Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- include/linux/srcu.h | 21 ++++++++++----------- include/linux/srcutree.h | 2 +- kernel/rcu/srcutree.c | 22 +++++++++++----------- 3 files changed, 22 insertions(+), 23 deletions(-) diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 835bbb2d1f88a..06728ef6f32a4 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -181,10 +181,9 @@ static inline int srcu_read_lock_held(const struct src= u_struct *ssp) #define SRCU_NMI_SAFE 0x2 =20 #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_TREE_SRCU) -void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe); +void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor); #else -static inline void srcu_check_nmi_safety(struct srcu_struct *ssp, - bool nmi_safe) { } +static inline void srcu_check_read_flavor(struct srcu_struct *ssp, int rea= d_flavor) { } #endif =20 =20 @@ -245,7 +244,7 @@ static inline int srcu_read_lock(struct srcu_struct *ss= p) __acquires(ssp) { int retval; =20 - srcu_check_nmi_safety(ssp, false); + srcu_check_read_flavor(ssp, false); retval =3D __srcu_read_lock(ssp); srcu_lock_acquire(&ssp->dep_map); return retval; @@ -262,7 +261,7 @@ static inline int srcu_read_lock_nmisafe(struct srcu_st= ruct *ssp) __acquires(ssp { int retval; =20 - srcu_check_nmi_safety(ssp, true); + srcu_check_read_flavor(ssp, true); retval =3D __srcu_read_lock_nmisafe(ssp); rcu_try_lock_acquire(&ssp->dep_map); return retval; @@ -274,7 +273,7 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acqui= res(ssp) { int retval; =20 - srcu_check_nmi_safety(ssp, false); + srcu_check_read_flavor(ssp, false); retval =3D __srcu_read_lock(ssp); return retval; } @@ -303,7 +302,7 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acqui= res(ssp) static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp) { WARN_ON_ONCE(in_nmi()); - srcu_check_nmi_safety(ssp, false); + srcu_check_read_flavor(ssp, false); return __srcu_read_lock(ssp); } =20 @@ -318,7 +317,7 @@ static inline void srcu_read_unlock(struct srcu_struct = *ssp, int idx) __releases(ssp) { WARN_ON_ONCE(idx & ~0x1); - srcu_check_nmi_safety(ssp, false); + srcu_check_read_flavor(ssp, false); srcu_lock_release(&ssp->dep_map); __srcu_read_unlock(ssp, idx); } @@ -334,7 +333,7 @@ static inline void srcu_read_unlock_nmisafe(struct srcu= _struct *ssp, int idx) __releases(ssp) { WARN_ON_ONCE(idx & ~0x1); - srcu_check_nmi_safety(ssp, true); + srcu_check_read_flavor(ssp, true); rcu_lock_release(&ssp->dep_map); __srcu_read_unlock_nmisafe(ssp, idx); } @@ -343,7 +342,7 @@ static inline void srcu_read_unlock_nmisafe(struct srcu= _struct *ssp, int idx) static inline notrace void srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp) { - srcu_check_nmi_safety(ssp, false); + srcu_check_read_flavor(ssp, false); __srcu_read_unlock(ssp, idx); } =20 @@ -360,7 +359,7 @@ static inline void srcu_up_read(struct srcu_struct *ssp= , int idx) { WARN_ON_ONCE(idx & ~0x1); WARN_ON_ONCE(in_nmi()); - srcu_check_nmi_safety(ssp, false); + srcu_check_read_flavor(ssp, false); __srcu_read_unlock(ssp, idx); } =20 diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index ed57598394de3..ab7d8d215b84b 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -25,7 +25,7 @@ struct srcu_data { /* Read-side state. */ atomic_long_t srcu_lock_count[2]; /* Locks per CPU. */ atomic_long_t srcu_unlock_count[2]; /* Unlocks per CPU. */ - int srcu_nmi_safety; /* NMI-safe srcu_struct structure? */ + int srcu_reader_flavor; /* Reader flavor for srcu_struct structure? */ =20 /* Update-side state. */ spinlock_t __private lock ____cacheline_internodealigned_in_smp; diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index e29c6cbffbcb0..18f2eae5e14bd 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -460,7 +460,7 @@ static unsigned long srcu_readers_unlock_idx(struct src= u_struct *ssp, int idx) =20 sum +=3D atomic_long_read(&cpuc->srcu_unlock_count[idx]); if (IS_ENABLED(CONFIG_PROVE_RCU)) - mask =3D mask | READ_ONCE(cpuc->srcu_nmi_safety); + mask =3D mask | READ_ONCE(cpuc->srcu_reader_flavor); } WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && (mask & (mask >> 1)), "Mixed NMI-safe readers for srcu_struct at %ps.\n", ssp); @@ -699,25 +699,25 @@ EXPORT_SYMBOL_GPL(cleanup_srcu_struct); =20 #ifdef CONFIG_PROVE_RCU /* - * Check for consistent NMI safety. + * Check for consistent reader flavor. */ -void srcu_check_nmi_safety(struct srcu_struct *ssp, bool nmi_safe) +void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor) { - int nmi_safe_mask =3D 1 << nmi_safe; - int old_nmi_safe_mask; + int reader_flavor_mask =3D 1 << read_flavor; + int old_reader_flavor_mask; struct srcu_data *sdp; =20 /* NMI-unsafe use in NMI is a bad sign */ - WARN_ON_ONCE(!nmi_safe && in_nmi()); + WARN_ON_ONCE(!read_flavor && in_nmi()); sdp =3D raw_cpu_ptr(ssp->sda); - old_nmi_safe_mask =3D READ_ONCE(sdp->srcu_nmi_safety); - if (!old_nmi_safe_mask) { - WRITE_ONCE(sdp->srcu_nmi_safety, nmi_safe_mask); + old_reader_flavor_mask =3D READ_ONCE(sdp->srcu_reader_flavor); + if (!old_reader_flavor_mask) { + WRITE_ONCE(sdp->srcu_reader_flavor, reader_flavor_mask); return; } - WARN_ONCE(old_nmi_safe_mask !=3D nmi_safe_mask, "CPU %d old state %d new = state %d\n", sdp->cpu, old_nmi_safe_mask, nmi_safe_mask); + WARN_ONCE(old_reader_flavor_mask !=3D reader_flavor_mask, "CPU %d old sta= te %d new state %d\n", sdp->cpu, old_reader_flavor_mask, reader_flavor_mask= ); } -EXPORT_SYMBOL_GPL(srcu_check_nmi_safety); +EXPORT_SYMBOL_GPL(srcu_check_read_flavor); #endif /* CONFIG_PROVE_RCU */ =20 /* --=20 2.40.1 From nobody Wed Nov 27 06:37:06 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 5A6241BFDFE; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; cv=none; b=ePT9IFfRwROBDYr+oMwk8AK4xA3h6e+K3fzqidS9k8MlsuP99048PidkrH2ZNsIcccKBdGWI+BB4fgc4JQQ17SJxV9NEpLbrIHK26AQc9MepTLUwq5mHXk9aMS1vN8WIwMkEzjHxE3rAUQsPlY/8ShLT/thAvWXqwKZd3lekNQw= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; c=relaxed/simple; bh=HtkA9wBw7Sojuw5HhHk7JjMMtDq6tne9Y9iMOe1hFF4=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=K+LpScnC3EGii6NfOgQ9jk15xHn7a3bt7b2U2qE+CJ88WBCNPkSWgElmXpTpvoGWnhbvXHF1QaYwyxVSz9UsxsINhg6DQjbNuCvddhf9guFGb6VxC2Qtd8yhjTEQRqCVO8MSdb2m3KLulUkv7wJr0QIDv7Gj/RwWoKIWGIJ8Np4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Ob2jLMg4; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Ob2jLMg4" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1463FC4CED1; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728668373; bh=HtkA9wBw7Sojuw5HhHk7JjMMtDq6tne9Y9iMOe1hFF4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ob2jLMg4ro6J/JB+s3BjG3i2e2uU3jB6u1ItK0YKX2XGOkVVVX9hAhmGcg9c8NWwI Xzvex1iXc4Lk5/XZJqY4SBRZLRusIroPNFGq4HP024arBgDozXDx5sIiyi7Qfz3H5V AqGTw9+PBZY2HW9KVXz+wk0B9J937n3ZBY8Zxt56SvSzk13n7ZdeSnC32sCYpWtaKK 4dQjAdP/Ahd3RFLqfscl8j/5wDB4oYeiRSTkVgrO5dqzOuKy2yi/3UXlMH4YiqIJDv 96A0e2dynnX0PykpHlWbZnWw1XQuFgoY21amh8HGLPX4/rT5jU2fvKrvijttYqDxCU ctPhmi/K01UGA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id A1D56CE0EBC; Fri, 11 Oct 2024 10:39:32 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH v2 rcu 04/13] srcu: Bit manipulation changes for additional reader flavor Date: Fri, 11 Oct 2024 10:39:22 -0700 Message-Id: <20241011173931.2050422-4-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> References: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Currently, there are only two flavors of readers, normal and NMI-safe. Very straightforward state updates suffice to check for erroneous mixing of reader flavors on a given srcu_struct structure. This commit upgrades the checking in preparation for the addition of light-weight (as in memory-barrier-free) readers. Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- kernel/rcu/srcutree.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 18f2eae5e14bd..abe55777c4335 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -462,7 +462,7 @@ static unsigned long srcu_readers_unlock_idx(struct src= u_struct *ssp, int idx) if (IS_ENABLED(CONFIG_PROVE_RCU)) mask =3D mask | READ_ONCE(cpuc->srcu_reader_flavor); } - WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && (mask & (mask >> 1)), + WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && (mask & (mask - 1)), "Mixed NMI-safe readers for srcu_struct at %ps.\n", ssp); return sum; } @@ -712,8 +712,9 @@ void srcu_check_read_flavor(struct srcu_struct *ssp, in= t read_flavor) sdp =3D raw_cpu_ptr(ssp->sda); old_reader_flavor_mask =3D READ_ONCE(sdp->srcu_reader_flavor); if (!old_reader_flavor_mask) { - WRITE_ONCE(sdp->srcu_reader_flavor, reader_flavor_mask); - return; + old_reader_flavor_mask =3D cmpxchg(&sdp->srcu_reader_flavor, 0, reader_f= lavor_mask); + if (!old_reader_flavor_mask) + return; } WARN_ONCE(old_reader_flavor_mask !=3D reader_flavor_mask, "CPU %d old sta= te %d new state %d\n", sdp->cpu, old_reader_flavor_mask, reader_flavor_mask= ); } --=20 2.40.1 From nobody Wed Nov 27 06:37:06 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7FE771C57A3; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; cv=none; b=OAUpBWoAumTrsArgjfTPP1QkidesVjQ+tys4H7QqraFNctc17YJmw9oYSKoX0kjb3gcSNQjuAbA1IF27Ar+UX01r/Z2eOYqM4y35ByvwpuBDToecrRSpCxGB4gDCoiuUG1gYmqt6YIDDkgSf4VmyD9r8/hWWSMJ8CwiswH12auA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; c=relaxed/simple; bh=6e6nFQakYcsfA7al8QMxHMj/HwDI3C+Crb6uuY7zJh4=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=ZjY3P3y6/HNzu2mht73gGJld9RMexYdCYgdxaUFZKvmC73S5mMyurYuy9BeNK9avGSuYBBtrDxbCj6IxZfjCt9Q8lfIca9O6CtLgz5gsE02/oEa2eHt8BM432cWchdXwaK/marzOvqoZawx86KFtz9hq0tSM88WbJ4W4yU/ixXI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=BdlZy6mA; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="BdlZy6mA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 1CE36C4CED3; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728668373; bh=6e6nFQakYcsfA7al8QMxHMj/HwDI3C+Crb6uuY7zJh4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BdlZy6mALy1GU/borUcN8FIa2bdBq7bZyracfBiSN17DxNTdNPgBRlLta1OgYIid7 l32HcssoCmzAplwm+N3MfAhtl+oiccsITiX9G7CHsiZnyYu+nYKczaddwpAkcxVHwV fnntxIzRaIfC21iPDchYIRVQwizCUxudRzA1L5FQaxdz4dhi+XS89XWn/4mj5BaMIK i+MoeUGFThKx69Q7IgTdkBzJlVlZDgX0nBe7lbDFctcDNGo+rhK9e7QMxOn4OYePyy x1D1/hm6CEYrF98hvr7rHPLmddpmOQi73tz8iBzQCh29UaFa/mu1YtrWVDPduGz0q2 2r8ML9aaFt4Eg== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id A490BCE0F51; Fri, 11 Oct 2024 10:39:32 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH v2 rcu 05/13] srcu: Standardize srcu_data pointers to "sdp" and similar Date: Fri, 11 Oct 2024 10:39:23 -0700 Message-Id: <20241011173931.2050422-5-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> References: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" This commit changes a few "cpuc" variables to "sdp" to align wiht usage elsewhere. Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- include/linux/srcu.h | 35 ++++++++++++++++++---------------- include/linux/srcutree.h | 4 ++++ kernel/rcu/srcutree.c | 41 ++++++++++++++++++++-------------------- 3 files changed, 44 insertions(+), 36 deletions(-) diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 06728ef6f32a4..84daaa33ea0ab 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -176,10 +176,6 @@ static inline int srcu_read_lock_held(const struct src= u_struct *ssp) =20 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */ =20 -#define SRCU_NMI_UNKNOWN 0x0 -#define SRCU_NMI_UNSAFE 0x1 -#define SRCU_NMI_SAFE 0x2 - #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_TREE_SRCU) void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor); #else @@ -235,16 +231,19 @@ static inline void srcu_check_read_flavor(struct srcu= _struct *ssp, int read_flav * a mutex that is held elsewhere while calling synchronize_srcu() or * synchronize_srcu_expedited(). * - * Note that srcu_read_lock() and the matching srcu_read_unlock() must - * occur in the same context, for example, it is illegal to invoke - * srcu_read_unlock() in an irq handler if the matching srcu_read_lock() - * was invoked in process context. + * The return value from srcu_read_lock() must be passed unaltered + * to the matching srcu_read_unlock(). Note that srcu_read_lock() and + * the matching srcu_read_unlock() must occur in the same context, for + * example, it is illegal to invoke srcu_read_unlock() in an irq handler + * if the matching srcu_read_lock() was invoked in process context. Or, + * for that matter to invoke srcu_read_unlock() from one task and the + * matching srcu_read_lock() from another. */ static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp) { int retval; =20 - srcu_check_read_flavor(ssp, false); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); retval =3D __srcu_read_lock(ssp); srcu_lock_acquire(&ssp->dep_map); return retval; @@ -256,12 +255,16 @@ static inline int srcu_read_lock(struct srcu_struct *= ssp) __acquires(ssp) * * Enter an SRCU read-side critical section, but in an NMI-safe manner. * See srcu_read_lock() for more information. + * + * If srcu_read_lock_nmisafe() is ever used on an srcu_struct structure, + * then none of the other flavors may be used, whether before, during, + * or after. */ static inline int srcu_read_lock_nmisafe(struct srcu_struct *ssp) __acquir= es(ssp) { int retval; =20 - srcu_check_read_flavor(ssp, true); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NMI); retval =3D __srcu_read_lock_nmisafe(ssp); rcu_try_lock_acquire(&ssp->dep_map); return retval; @@ -273,7 +276,7 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acqui= res(ssp) { int retval; =20 - srcu_check_read_flavor(ssp, false); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); retval =3D __srcu_read_lock(ssp); return retval; } @@ -302,7 +305,7 @@ srcu_read_lock_notrace(struct srcu_struct *ssp) __acqui= res(ssp) static inline int srcu_down_read(struct srcu_struct *ssp) __acquires(ssp) { WARN_ON_ONCE(in_nmi()); - srcu_check_read_flavor(ssp, false); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); return __srcu_read_lock(ssp); } =20 @@ -317,7 +320,7 @@ static inline void srcu_read_unlock(struct srcu_struct = *ssp, int idx) __releases(ssp) { WARN_ON_ONCE(idx & ~0x1); - srcu_check_read_flavor(ssp, false); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); srcu_lock_release(&ssp->dep_map); __srcu_read_unlock(ssp, idx); } @@ -333,7 +336,7 @@ static inline void srcu_read_unlock_nmisafe(struct srcu= _struct *ssp, int idx) __releases(ssp) { WARN_ON_ONCE(idx & ~0x1); - srcu_check_read_flavor(ssp, true); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NMI); rcu_lock_release(&ssp->dep_map); __srcu_read_unlock_nmisafe(ssp, idx); } @@ -342,7 +345,7 @@ static inline void srcu_read_unlock_nmisafe(struct srcu= _struct *ssp, int idx) static inline notrace void srcu_read_unlock_notrace(struct srcu_struct *ssp, int idx) __releases(ssp) { - srcu_check_read_flavor(ssp, false); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); __srcu_read_unlock(ssp, idx); } =20 @@ -359,7 +362,7 @@ static inline void srcu_up_read(struct srcu_struct *ssp= , int idx) { WARN_ON_ONCE(idx & ~0x1); WARN_ON_ONCE(in_nmi()); - srcu_check_read_flavor(ssp, false); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_NORMAL); __srcu_read_unlock(ssp, idx); } =20 diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index ab7d8d215b84b..79ad809c7f035 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -43,6 +43,10 @@ struct srcu_data { struct srcu_struct *ssp; }; =20 +/* Values for ->srcu_reader_flavor. */ +#define SRCU_READ_FLAVOR_NORMAL 0x1 // srcu_read_lock(). +#define SRCU_READ_FLAVOR_NMI 0x2 // srcu_read_lock_nmisafe(). + /* * Node in SRCU combining tree, similar in function to rcu_data. */ diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index abe55777c4335..4c51be484b48a 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -438,9 +438,9 @@ static unsigned long srcu_readers_lock_idx(struct srcu_= struct *ssp, int idx) unsigned long sum =3D 0; =20 for_each_possible_cpu(cpu) { - struct srcu_data *cpuc =3D per_cpu_ptr(ssp->sda, cpu); + struct srcu_data *sdp =3D per_cpu_ptr(ssp->sda, cpu); =20 - sum +=3D atomic_long_read(&cpuc->srcu_lock_count[idx]); + sum +=3D atomic_long_read(&sdp->srcu_lock_count[idx]); } return sum; } @@ -456,14 +456,14 @@ static unsigned long srcu_readers_unlock_idx(struct s= rcu_struct *ssp, int idx) unsigned long sum =3D 0; =20 for_each_possible_cpu(cpu) { - struct srcu_data *cpuc =3D per_cpu_ptr(ssp->sda, cpu); + struct srcu_data *sdp =3D per_cpu_ptr(ssp->sda, cpu); =20 - sum +=3D atomic_long_read(&cpuc->srcu_unlock_count[idx]); + sum +=3D atomic_long_read(&sdp->srcu_unlock_count[idx]); if (IS_ENABLED(CONFIG_PROVE_RCU)) - mask =3D mask | READ_ONCE(cpuc->srcu_reader_flavor); + mask =3D mask | READ_ONCE(sdp->srcu_reader_flavor); } WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && (mask & (mask - 1)), - "Mixed NMI-safe readers for srcu_struct at %ps.\n", ssp); + "Mixed reader flavors for srcu_struct at %ps.\n", ssp); return sum; } =20 @@ -564,12 +564,12 @@ static bool srcu_readers_active(struct srcu_struct *s= sp) unsigned long sum =3D 0; =20 for_each_possible_cpu(cpu) { - struct srcu_data *cpuc =3D per_cpu_ptr(ssp->sda, cpu); + struct srcu_data *sdp =3D per_cpu_ptr(ssp->sda, cpu); =20 - sum +=3D atomic_long_read(&cpuc->srcu_lock_count[0]); - sum +=3D atomic_long_read(&cpuc->srcu_lock_count[1]); - sum -=3D atomic_long_read(&cpuc->srcu_unlock_count[0]); - sum -=3D atomic_long_read(&cpuc->srcu_unlock_count[1]); + sum +=3D atomic_long_read(&sdp->srcu_lock_count[0]); + sum +=3D atomic_long_read(&sdp->srcu_lock_count[1]); + sum -=3D atomic_long_read(&sdp->srcu_unlock_count[0]); + sum -=3D atomic_long_read(&sdp->srcu_unlock_count[1]); } return sum; } @@ -703,20 +703,21 @@ EXPORT_SYMBOL_GPL(cleanup_srcu_struct); */ void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor) { - int reader_flavor_mask =3D 1 << read_flavor; - int old_reader_flavor_mask; + int old_read_flavor; struct srcu_data *sdp; =20 - /* NMI-unsafe use in NMI is a bad sign */ - WARN_ON_ONCE(!read_flavor && in_nmi()); + /* NMI-unsafe use in NMI is a bad sign, as is multi-bit read_flavor value= s. */ + WARN_ON_ONCE((read_flavor !=3D SRCU_READ_FLAVOR_NMI) && in_nmi()); + WARN_ON_ONCE(read_flavor & (read_flavor - 1)); + sdp =3D raw_cpu_ptr(ssp->sda); - old_reader_flavor_mask =3D READ_ONCE(sdp->srcu_reader_flavor); - if (!old_reader_flavor_mask) { - old_reader_flavor_mask =3D cmpxchg(&sdp->srcu_reader_flavor, 0, reader_f= lavor_mask); 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McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , kernel test robot , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH v2 rcu 06/13] srcu: Add srcu_read_lock_lite() and srcu_read_unlock_lite() Date: Fri, 11 Oct 2024 10:39:24 -0700 Message-Id: <20241011173931.2050422-6-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> References: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" This patch adds srcu_read_lock_lite() and srcu_read_unlock_lite(), which dispense with the read-side smp_mb() but also are restricted to code regions that RCU is watching. If a given srcu_struct structure uses srcu_read_lock_lite() and srcu_read_unlock_lite(), it is not permitted to use any other SRCU read-side marker, before, during, or after. Another price of light-weight readers is heavier weight grace periods. Such readers mean that SRCU grace periods on srcu_struct structures used by light-weight readers will incur at least two calls to synchronize_rcu(). In addition, normal SRCU grace periods for light-weight-reader srcu_struct structures never auto-expedite. Note that expedited SRCU grace periods for light-weight-reader srcu_struct structures still invoke synchronize_rcu(), not synchronize_srcu_expedited(). Something about wishing to keep the IPIs down to a dull roar. The srcu_read_lock_lite() and srcu_read_unlock_lite() functions may not (repeat, *not*) be used from NMI handlers, but if this is needed, an additional flavor of SRCU reader can be added by some future commit. [ paulmck: Apply Alexei Starovoitov expediting feedback. ] [ paulmck: Apply kernel test robot feedback. ] Signed-off-by: Paul E. McKenney Tested-by: kernel test robot Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- include/linux/srcu.h | 51 ++++++++++++++++++++++++- include/linux/srcutree.h | 1 + kernel/rcu/srcutree.c | 82 ++++++++++++++++++++++++++++++++++------ 3 files changed, 122 insertions(+), 12 deletions(-) diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 84daaa33ea0ab..4ba96e2cfa405 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -56,6 +56,13 @@ void call_srcu(struct srcu_struct *ssp, struct rcu_head = *head, void cleanup_srcu_struct(struct srcu_struct *ssp); int __srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp); void __srcu_read_unlock(struct srcu_struct *ssp, int idx) __releases(ssp); +#ifdef CONFIG_TINY_SRCU +#define __srcu_read_lock_lite __srcu_read_lock +#define __srcu_read_unlock_lite __srcu_read_unlock +#else // #ifdef CONFIG_TINY_SRCU +int __srcu_read_lock_lite(struct srcu_struct *ssp) __acquires(ssp); +void __srcu_read_unlock_lite(struct srcu_struct *ssp, int idx) __releases(= ssp); +#endif // #else // #ifdef CONFIG_TINY_SRCU void synchronize_srcu(struct srcu_struct *ssp); =20 #define SRCU_GET_STATE_COMPLETED 0x1 @@ -179,7 +186,7 @@ static inline int srcu_read_lock_held(const struct srcu= _struct *ssp) #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_TREE_SRCU) void srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor); #else -static inline void srcu_check_read_flavor(struct srcu_struct *ssp, int rea= d_flavor) { } +#define srcu_check_read_flavor(ssp, read_flavor) do { } while (0) #endif =20 =20 @@ -249,6 +256,32 @@ static inline int srcu_read_lock(struct srcu_struct *s= sp) __acquires(ssp) return retval; } =20 +/** + * srcu_read_lock_lite - register a new reader for an SRCU-protected struc= ture. + * @ssp: srcu_struct in which to register the new reader. + * + * Enter an SRCU read-side critical section, but for a light-weight + * smp_mb()-free reader. See srcu_read_lock() for more information. + * + * If srcu_read_lock_lite() is ever used on an srcu_struct structure, + * then none of the other flavors may be used, whether before, during, + * or after. Note that grace-period auto-expediting is disabled for _lite + * srcu_struct structures because auto-expedited grace periods invoke + * synchronize_rcu_expedited(), IPIs and all. + * + * Note that srcu_read_lock_lite() can be invoked only from those contexts + * where RCU is watching. Otherwise, lockdep will complain. + */ +static inline int srcu_read_lock_lite(struct srcu_struct *ssp) __acquires(= ssp) +{ + int retval; + + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_LITE); + retval =3D __srcu_read_lock_lite(ssp); + rcu_try_lock_acquire(&ssp->dep_map); + return retval; +} + /** * srcu_read_lock_nmisafe - register a new reader for an SRCU-protected st= ructure. * @ssp: srcu_struct in which to register the new reader. @@ -325,6 +358,22 @@ static inline void srcu_read_unlock(struct srcu_struct= *ssp, int idx) __srcu_read_unlock(ssp, idx); } =20 +/** + * srcu_read_unlock_lite - unregister a old reader from an SRCU-protected = structure. + * @ssp: srcu_struct in which to unregister the old reader. + * @idx: return value from corresponding srcu_read_lock(). + * + * Exit a light-weight SRCU read-side critical section. + */ +static inline void srcu_read_unlock_lite(struct srcu_struct *ssp, int idx) + __releases(ssp) +{ + WARN_ON_ONCE(idx & ~0x1); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_LITE); + srcu_lock_release(&ssp->dep_map); + __srcu_read_unlock(ssp, idx); +} + /** * srcu_read_unlock_nmisafe - unregister a old reader from an SRCU-protect= ed structure. * @ssp: srcu_struct in which to unregister the old reader. diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index 79ad809c7f035..8074138cbd624 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -46,6 +46,7 @@ struct srcu_data { /* Values for ->srcu_reader_flavor. */ #define SRCU_READ_FLAVOR_NORMAL 0x1 // srcu_read_lock(). #define SRCU_READ_FLAVOR_NMI 0x2 // srcu_read_lock_nmisafe(). +#define SRCU_READ_FLAVOR_LITE 0x4 // srcu_read_lock_lite(). =20 /* * Node in SRCU combining tree, similar in function to rcu_data. diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index 4c51be484b48a..bf51758cf4a64 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -429,20 +429,29 @@ static bool srcu_gp_is_expedited(struct srcu_struct *= ssp) } =20 /* - * Returns approximate total of the readers' ->srcu_lock_count[] values - * for the rank of per-CPU counters specified by idx. + * Computes approximate total of the readers' ->srcu_lock_count[] values + * for the rank of per-CPU counters specified by idx, and returns true if + * the caller did the proper barrier (gp), and if the count of the locks + * matches that of the unlocks passed in. */ -static unsigned long srcu_readers_lock_idx(struct srcu_struct *ssp, int id= x) +static bool srcu_readers_lock_idx(struct srcu_struct *ssp, int idx, bool g= p, unsigned long unlocks) { int cpu; + unsigned long mask =3D 0; unsigned long sum =3D 0; =20 for_each_possible_cpu(cpu) { struct srcu_data *sdp =3D per_cpu_ptr(ssp->sda, cpu); =20 sum +=3D atomic_long_read(&sdp->srcu_lock_count[idx]); + if (IS_ENABLED(CONFIG_PROVE_RCU)) + mask =3D mask | READ_ONCE(sdp->srcu_reader_flavor); } - return sum; + WARN_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && (mask & (mask - 1)), + "Mixed reader flavors for srcu_struct at %ps.\n", ssp); + if (mask & SRCU_READ_FLAVOR_LITE && !gp) + return false; + return sum =3D=3D unlocks; } =20 /* @@ -473,6 +482,7 @@ static unsigned long srcu_readers_unlock_idx(struct src= u_struct *ssp, int idx) */ static bool srcu_readers_active_idx_check(struct srcu_struct *ssp, int idx) { + bool did_gp =3D !!(raw_cpu_read(ssp->sda->srcu_reader_flavor) & SRCU_READ= _FLAVOR_LITE); unsigned long unlocks; =20 unlocks =3D srcu_readers_unlock_idx(ssp, idx); @@ -482,13 +492,16 @@ static bool srcu_readers_active_idx_check(struct srcu= _struct *ssp, int idx) * unlock is counted. Needs to be a smp_mb() as the read side may * contain a read from a variable that is written to before the * synchronize_srcu() in the write side. In this case smp_mb()s - * A and B act like the store buffering pattern. + * A and B (or X and Y) act like the store buffering pattern. * - * This smp_mb() also pairs with smp_mb() C to prevent accesses - * after the synchronize_srcu() from being executed before the - * grace period ends. + * This smp_mb() also pairs with smp_mb() C (or, in the case of X, + * Z) to prevent accesses after the synchronize_srcu() from being + * executed before the grace period ends. */ - smp_mb(); /* A */ + if (!did_gp) + smp_mb(); /* A */ + else + synchronize_rcu(); /* X */ =20 /* * If the locks are the same as the unlocks, then there must have @@ -546,7 +559,7 @@ static bool srcu_readers_active_idx_check(struct srcu_s= truct *ssp, int idx) * which are unlikely to be configured with an address space fully * populated with memory, at least not anytime soon. */ - return srcu_readers_lock_idx(ssp, idx) =3D=3D unlocks; + return srcu_readers_lock_idx(ssp, idx, did_gp, unlocks); } =20 /** @@ -750,6 +763,47 @@ void __srcu_read_unlock(struct srcu_struct *ssp, int i= dx) } EXPORT_SYMBOL_GPL(__srcu_read_unlock); =20 +/* + * Counts the new reader in the appropriate per-CPU element of the + * srcu_struct. Returns an index that must be passed to the matching + * srcu_read_unlock_lite(). + * + * Note that this_cpu_inc() is an RCU read-side critical section either + * because it disables interrupts, because it is a single instruction, + * or because it is a read-modify-write atomic operation, depending on + * the whims of the architecture. + */ +int __srcu_read_lock_lite(struct srcu_struct *ssp) +{ + int idx; + + RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock= _lite()."); + idx =3D READ_ONCE(ssp->srcu_idx) & 0x1; + this_cpu_inc(ssp->sda->srcu_lock_count[idx].counter); /* Y */ + barrier(); /* Avoid leaking the critical section. */ + return idx; +} +EXPORT_SYMBOL_GPL(__srcu_read_lock_lite); + +/* + * Removes the count for the old reader from the appropriate + * per-CPU element of the srcu_struct. Note that this may well be a + * different CPU than that which was incremented by the corresponding + * srcu_read_lock_lite(), but it must be within the same task. + * + * Note that this_cpu_inc() is an RCU read-side critical section either + * because it disables interrupts, because it is a single instruction, + * or because it is a read-modify-write atomic operation, depending on + * the whims of the architecture. + */ +void __srcu_read_unlock_lite(struct srcu_struct *ssp, int idx) +{ + barrier(); /* Avoid leaking the critical section. */ + this_cpu_inc(ssp->sda->srcu_unlock_count[idx].counter); /* Z */ + RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_unlo= ck_lite()."); +} +EXPORT_SYMBOL_GPL(__srcu_read_unlock_lite); + #ifdef CONFIG_NEED_SRCU_NMI_SAFE =20 /* @@ -1134,6 +1188,8 @@ static void srcu_flip(struct srcu_struct *ssp) * it stays until either (1) Compilers learn about this sort of * control dependency or (2) Some production workload running on * a production system is unduly delayed by this slowpath smp_mb(). + * Except for _lite() readers, where it is inoperative, which + * means that it is a good thing that it is redundant. */ smp_mb(); /* E */ /* Pairs with B and C. */ =20 @@ -1152,7 +1208,8 @@ static void srcu_flip(struct srcu_struct *ssp) =20 /* * If SRCU is likely idle, in other words, the next SRCU grace period - * should be expedited, return true, otherwise return false. + * should be expedited, return true, otherwise return false. Except that + * in the presence of _lite() readers, always return false. * * Note that it is OK for several current from-idle requests for a new * grace period from idle to specify expediting because they will all end @@ -1181,6 +1238,9 @@ static bool srcu_should_expedite(struct srcu_struct *= ssp) unsigned long tlast; =20 check_init_srcu_struct(ssp); + /* If _lite() readers, don't do unsolicited expediting. */ + if (this_cpu_read(ssp->sda->srcu_reader_flavor) & SRCU_READ_FLAVOR_LITE) + return false; /* If the local srcu_data structure has callbacks, not idle. */ sdp =3D raw_cpu_ptr(ssp->sda); spin_lock_irqsave_rcu_node(sdp, flags); --=20 2.40.1 From nobody Wed Nov 27 06:37:06 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ACF671C8FCE; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; cv=none; b=ZxrrvSR5Xux1rDGTa5JnBRzYDQ54zASwW0VuyjUfDCAGBwKGni2oeEuRvylVVwFr6rjZVnM5bCeVjte/HhpMTlWBmh1kVaSpPc5IDgeMBvWJfrl333+f6ONXs6VVrLZhadrer12I0aZey4pNKLRyGWpdtqMUJduih2DTgtw8fSc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; c=relaxed/simple; bh=MCTM0QcTKx5V+XLmwCnRaQM2SyFIPw4fWJwP26eLAXM=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=LEW/2fU68pDmO94Q40F255arN1uE6Ntw7wrET6FgwQHruyyamH3cfw/XXwEj8i+tmlSf3DVFui48zYz8+bDztLJtZlMN21yGEf2lWNSHaSzhQfEom9bBChvAXNn5TyREPBtSkEuCk9JyDz6mNxc+JzvE5talij1cUsPxy2Y55eI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=Q5nGsLel; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="Q5nGsLel" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 52C25C4CEDD; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728668373; bh=MCTM0QcTKx5V+XLmwCnRaQM2SyFIPw4fWJwP26eLAXM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Q5nGsLel9UcgHr9oRnPYIopnvb0NbwLyaKRTUL+sASoRmiI3x6jjqCrKtmjrba1rY TK0tlbD/PByrxhG7wN3L3W0zrIQz1eXELmvTUgLLLw6CPmGuXfyEH5XbEuyGsbFwe6 p/wdFmZY1HlIwxSHUtRQ+mkGs1dUvTB7JM8VXR1qwlhmlJByl7jegP9FKC2Z1UZ5qS pG6sGLirJQLnXNv58xcAU9rraTwqH7HtrPQ5kBm5W0u1crRTajESUWAziw7S7phvnM vatepLSiboZKNLQYRIhDxtoNa13xBRA+GiYHpZZ/oYvaq5ctIJD/qjjmK84JsFjnAk BR2o/xy/khshg== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id AA778CE0F56; Fri, 11 Oct 2024 10:39:32 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH v2 rcu 07/13] srcu: Allow inlining of __srcu_read_{,un}lock_lite() Date: Fri, 11 Oct 2024 10:39:25 -0700 Message-Id: <20241011173931.2050422-7-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> References: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" This commit moves __srcu_read_lock_lite() and __srcu_read_unlock_lite() into include/linux/srcu.h and marks them "static inline" so that they can be inlined into srcu_read_lock_lite() and srcu_read_unlock_lite(), respectively. They are not hand-inlined due to Tree SRCU and Tiny SRCU having different implementations. The earlier removal of smp_mb() combined with the inlining produce significant single-percentage performance wins. Link: https://lore.kernel.org/all/CAEf4BzYgiNmSb=3DZKQ65tm6nJDi1UX2Gq26cdHS= H1mPwXJYZj5g@mail.gmail.com/ Reported-by: Alexei Starovoitov Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- include/linux/srcutree.h | 39 ++++++++++++++++++++++++++++++++++++++ kernel/rcu/srcutree.c | 41 ---------------------------------------- 2 files changed, 39 insertions(+), 41 deletions(-) diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index 8074138cbd624..778eb61542e18 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -209,4 +209,43 @@ void synchronize_srcu_expedited(struct srcu_struct *ss= p); void srcu_barrier(struct srcu_struct *ssp); void srcu_torture_stats_print(struct srcu_struct *ssp, char *tt, char *tf); =20 +/* + * Counts the new reader in the appropriate per-CPU element of the + * srcu_struct. Returns an index that must be passed to the matching + * srcu_read_unlock_lite(). + * + * Note that this_cpu_inc() is an RCU read-side critical section either + * because it disables interrupts, because it is a single instruction, + * or because it is a read-modify-write atomic operation, depending on + * the whims of the architecture. + */ +static inline int __srcu_read_lock_lite(struct srcu_struct *ssp) +{ + int idx; + + RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock= _lite()."); + idx =3D READ_ONCE(ssp->srcu_idx) & 0x1; + this_cpu_inc(ssp->sda->srcu_lock_count[idx].counter); /* Y */ + barrier(); /* Avoid leaking the critical section. */ + return idx; +} + +/* + * Removes the count for the old reader from the appropriate + * per-CPU element of the srcu_struct. Note that this may well be a + * different CPU than that which was incremented by the corresponding + * srcu_read_lock_lite(), but it must be within the same task. + * + * Note that this_cpu_inc() is an RCU read-side critical section either + * because it disables interrupts, because it is a single instruction, + * or because it is a read-modify-write atomic operation, depending on + * the whims of the architecture. + */ +static inline void __srcu_read_unlock_lite(struct srcu_struct *ssp, int id= x) +{ + barrier(); /* Avoid leaking the critical section. */ + this_cpu_inc(ssp->sda->srcu_unlock_count[idx].counter); /* Z */ + RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_unlo= ck_lite()."); +} + #endif diff --git a/kernel/rcu/srcutree.c b/kernel/rcu/srcutree.c index bf51758cf4a64..07147efcb64d3 100644 --- a/kernel/rcu/srcutree.c +++ b/kernel/rcu/srcutree.c @@ -763,47 +763,6 @@ void __srcu_read_unlock(struct srcu_struct *ssp, int i= dx) } EXPORT_SYMBOL_GPL(__srcu_read_unlock); =20 -/* - * Counts the new reader in the appropriate per-CPU element of the - * srcu_struct. Returns an index that must be passed to the matching - * srcu_read_unlock_lite(). - * - * Note that this_cpu_inc() is an RCU read-side critical section either - * because it disables interrupts, because it is a single instruction, - * or because it is a read-modify-write atomic operation, depending on - * the whims of the architecture. - */ -int __srcu_read_lock_lite(struct srcu_struct *ssp) -{ - int idx; - - RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock= _lite()."); - idx =3D READ_ONCE(ssp->srcu_idx) & 0x1; - this_cpu_inc(ssp->sda->srcu_lock_count[idx].counter); /* Y */ - barrier(); /* Avoid leaking the critical section. */ - return idx; -} -EXPORT_SYMBOL_GPL(__srcu_read_lock_lite); - -/* - * Removes the count for the old reader from the appropriate - * per-CPU element of the srcu_struct. Note that this may well be a - * different CPU than that which was incremented by the corresponding - * srcu_read_lock_lite(), but it must be within the same task. - * - * Note that this_cpu_inc() is an RCU read-side critical section either - * because it disables interrupts, because it is a single instruction, - * or because it is a read-modify-write atomic operation, depending on - * the whims of the architecture. - */ -void __srcu_read_unlock_lite(struct srcu_struct *ssp, int idx) -{ - barrier(); /* Avoid leaking the critical section. */ - this_cpu_inc(ssp->sda->srcu_unlock_count[idx].counter); /* Z */ - RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_unlo= ck_lite()."); -} -EXPORT_SYMBOL_GPL(__srcu_read_unlock_lite); - #ifdef CONFIG_NEED_SRCU_NMI_SAFE =20 /* --=20 2.40.1 From nobody Wed Nov 27 06:37:06 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AA1661C8FB7; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; cv=none; b=GFFUBO/TJ5HwdnPYergrsNstlJQzfwLptW7/cMY7U8BhknmtBj2e4evV+Ve3oa7zxgegWyCHvp2VGo9e5UcYyRTsm7dhLgAVsmoUBJwbW0DQq5R2UEuXBEKDQ4hOYNjZIvJnDPYI8omhxpRzlr3o2hgzuBlsygCzr+MTWOVS1A8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; c=relaxed/simple; bh=455xAJUPKkl1YHsvTg2vxb9TRAoSDc2shVSbJO8e+tM=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=YDOYMV2mfhoe/6fCAx9vkOauQkEOEJ9mwQ8abpLzENPaVts1u0Mphr3xnPGK9YyinLMcksXmvyVzhKvI2GtNLzHeDBz+xyYpay/sPr5W/xjl1UzwqCJURE853qL4ctxwf7Ueba0XOGhTMdCkB0bvbQiXvz1oFJfFXRYOHB8K/9Q= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oDtQkEWq; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="oDtQkEWq" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 535BEC4CEDE; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728668373; bh=455xAJUPKkl1YHsvTg2vxb9TRAoSDc2shVSbJO8e+tM=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=oDtQkEWqbfF2aBZSfwRk6rOZWwfnqgfDE/1vfh+wqp6jg0VTYvUuBg5V7Tqx38vJ1 V5sRhogZmduaIC9XOq5gMskm+EZmqAZYdlyJ2ToXlF8SR/f9Cd1T8K0Gf1jDJFiD4L txrJwQ/aUy3v6XaEQhhRWSlwjJxEHKOUhMrss6yRuco5QrRo4sy2+0Hra5vIaSMQRi 00DvtPdq8nV0uJije9ihzFH5J1vlTVTxpAa69rQiealmvbaljUIZXlYJyio9BkKq4g wNJ9i4NtAMTB/v++uaj+R7N3ewIy8eScVYDdDKS1JWneA2wHPSu99tKwVmTWkkpwXY jl0Da52aCTMNQ== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id AD9B0CE0F7D; Fri, 11 Oct 2024 10:39:32 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH v2 rcu 08/13] rcutorture: Expand RCUTORTURE_RDR_MASK_[12] to eight bits Date: Fri, 11 Oct 2024 10:39:26 -0700 Message-Id: <20241011173931.2050422-8-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> References: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" This commit prepares for testing of multiple SRCU reader flavors by expanding RCUTORTURE_RDR_MASK_1 and RCUTORTURE_RDR_MASK_2 from a single bit to eight bits, allowing them to accommodate the return values from multiple calls to srcu_read_lock*(). This will in turn permit better testing coverage for these SRCU reader flavors, including testing of the diagnostics for inproper use of mixed reader flavors. Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- kernel/rcu/rcutorture.c | 28 ++++++++++++++-------------- 1 file changed, 14 insertions(+), 14 deletions(-) diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index bb75dbf5c800c..f96ab98f8182f 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -57,9 +57,9 @@ MODULE_AUTHOR("Paul E. McKenney a= nd Josh Triplett extendables field, extendables param, and related definition= s. */ #define RCUTORTURE_RDR_SHIFT_1 8 /* Put SRCU index in upper bits. */ -#define RCUTORTURE_RDR_MASK_1 (1 << RCUTORTURE_RDR_SHIFT_1) -#define RCUTORTURE_RDR_SHIFT_2 9 /* Put SRCU index in upper bits. */ -#define RCUTORTURE_RDR_MASK_2 (1 << RCUTORTURE_RDR_SHIFT_2) +#define RCUTORTURE_RDR_MASK_1 (0xff << RCUTORTURE_RDR_SHIFT_1) +#define RCUTORTURE_RDR_SHIFT_2 16 /* Put SRCU index in upper bits. */ +#define RCUTORTURE_RDR_MASK_2 (0xff << RCUTORTURE_RDR_SHIFT_2) #define RCUTORTURE_RDR_BH 0x01 /* Extend readers by disabling bh. */ #define RCUTORTURE_RDR_IRQ 0x02 /* ... disabling interrupts. */ #define RCUTORTURE_RDR_PREEMPT 0x04 /* ... disabling preemption. */ @@ -71,6 +71,9 @@ MODULE_AUTHOR("Paul E. McKenney a= nd Josh Triplett > RCUTORTURE_RDR_SHIFT_2) > 1); + WARN_ON_ONCE(idxold2 & ~RCUTORTURE_RDR_ALLBITS); rtrsp->rt_readstate =3D newstate; =20 /* First, put new protection in place to avoid critical-section gap. */ @@ -1835,9 +1838,9 @@ static void rcutorture_one_extend(int *readstate, int= newstate, if (statesnew & RCUTORTURE_RDR_SCHED) rcu_read_lock_sched(); if (statesnew & RCUTORTURE_RDR_RCU_1) - idxnew1 =3D (cur_ops->readlock() & 0x1) << RCUTORTURE_RDR_SHIFT_1; + idxnew1 =3D (cur_ops->readlock() << RCUTORTURE_RDR_SHIFT_1) & RCUTORTURE= _RDR_MASK_1; if (statesnew & RCUTORTURE_RDR_RCU_2) - idxnew2 =3D (cur_ops->readlock() & 0x1) << RCUTORTURE_RDR_SHIFT_2; + idxnew2 =3D (cur_ops->readlock() << RCUTORTURE_RDR_SHIFT_2) & RCUTORTURE= _RDR_MASK_2; =20 /* * Next, remove old protection, in decreasing order of strength @@ -1857,7 +1860,7 @@ static void rcutorture_one_extend(int *readstate, int= newstate, if (statesold & RCUTORTURE_RDR_RBH) rcu_read_unlock_bh(); if (statesold & RCUTORTURE_RDR_RCU_2) { - cur_ops->readunlock((idxold2 >> RCUTORTURE_RDR_SHIFT_2) & 0x1); + cur_ops->readunlock((idxold2 & RCUTORTURE_RDR_MASK_2) >> RCUTORTURE_RDR_= SHIFT_2); WARN_ON_ONCE(idxnew2 !=3D -1); idxold2 =3D 0; } @@ -1867,7 +1870,7 @@ static void rcutorture_one_extend(int *readstate, int= newstate, lockit =3D !cur_ops->no_pi_lock && !statesnew && !(torture_random(trsp) = & 0xffff); if (lockit) raw_spin_lock_irqsave(¤t->pi_lock, flags); - cur_ops->readunlock((idxold1 >> RCUTORTURE_RDR_SHIFT_1) & 0x1); + cur_ops->readunlock((idxold1 & RCUTORTURE_RDR_MASK_1) >> RCUTORTURE_RDR_= SHIFT_1); WARN_ON_ONCE(idxnew1 !=3D -1); idxold1 =3D 0; if (lockit) @@ -1882,16 +1885,13 @@ static void rcutorture_one_extend(int *readstate, i= nt newstate, if (idxnew1 =3D=3D -1) idxnew1 =3D idxold1 & RCUTORTURE_RDR_MASK_1; WARN_ON_ONCE(idxnew1 < 0); - if (WARN_ON_ONCE((idxnew1 >> RCUTORTURE_RDR_SHIFT_1) > 1)) - pr_info("Unexpected idxnew1 value of %#x\n", idxnew1); if (idxnew2 =3D=3D -1) idxnew2 =3D idxold2 & RCUTORTURE_RDR_MASK_2; WARN_ON_ONCE(idxnew2 < 0); - WARN_ON_ONCE((idxnew2 >> RCUTORTURE_RDR_SHIFT_2) > 1); *readstate =3D idxnew1 | idxnew2 | newstate; WARN_ON_ONCE(*readstate < 0); - if (WARN_ON_ONCE((*readstate >> RCUTORTURE_RDR_SHIFT_2) > 1)) - pr_info("Unexpected idxnew2 value of %#x\n", idxnew2); + if (WARN_ON_ONCE(*readstate & ~RCUTORTURE_RDR_ALLBITS)) + pr_info("Unexpected readstate value of %#x\n", *readstate); } =20 /* Return the biggest extendables mask given current RCU and boot paramete= rs. */ @@ -1916,7 +1916,7 @@ rcutorture_extend_mask(int oldmask, struct torture_ra= ndom_state *trsp) unsigned long preempts_irq =3D preempts | RCUTORTURE_RDR_IRQ; unsigned long bhs =3D RCUTORTURE_RDR_BH | RCUTORTURE_RDR_RBH; =20 - WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT_1); + WARN_ON_ONCE(mask >> RCUTORTURE_RDR_SHIFT_1); // Can't have reader idx b= its. /* Mostly only one bit (need preemption!), sometimes lots of bits. */ if (!(randmask1 & 0x7)) mask =3D mask & randmask2; --=20 2.40.1 From nobody Wed Nov 27 06:37:06 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AB8691C8FC1; 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dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="qWt70X3v" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5471AC4CEE0; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728668373; bh=USWy1f2+MRE4E6Ag+HiaCUvOKEVnE9SJTDypoSyYrTo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qWt70X3vWL4k1++QjbqhK9UTXcYfoXrqaN3XJc2cMveljYcrGtmmVMtfq4zYc1jgp dAc7XV0/Vj1QouUrgvGS9ytfnOkFnaVAiWd7/QvSOHo/GbggKfkhSEMm/FmG2pD4CZ Te9OmCZCqufJ0miu62e84WhJClzHpmYoHJQ6dCxXQdWr8uADAYN73WLbkdcNTm6GuB N5aUJRSNfJvJ1WGY8ib8FHlpkXgpx89wJprESjVSy+Frj98gaWgXDRwyHM+RV46Lab ojj9QPzPhfRH8jKojCu37UiLAKCUZYFtDEeDiaVm/bGjy0LDrP82erJlflQhFoqigq dxXb65Zf5uFCw== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id B037ECE0F96; Fri, 11 Oct 2024 10:39:32 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH v2 rcu 09/13] rcutorture: Add reader_flavor parameter for SRCU readers Date: Fri, 11 Oct 2024 10:39:27 -0700 Message-Id: <20241011173931.2050422-9-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> References: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" This commit adds an rcutorture.reader_flavor parameter whose bits correspond to reader flavors. For example, SRCU's readers are 0x1 for normal and 0x2 for NMI-safe. Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- .../admin-guide/kernel-parameters.txt | 8 +++++ kernel/rcu/rcutorture.c | 30 ++++++++++++++----- 2 files changed, 30 insertions(+), 8 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentatio= n/admin-guide/kernel-parameters.txt index 1518343bbe223..52922727006fc 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5426,6 +5426,14 @@ The delay, in seconds, between successive read-then-exit testing episodes. =20 + rcutorture.reader_flavor=3D [KNL] + A bit mask indicating which readers to use. + If there is more than one bit set, the readers + are entered from low-order bit up, and are + exited in the opposite order. For SRCU, the + 0x1 bit is normal readers and the 0x2 bit is + for NMI-safe readers. + rcutorture.shuffle_interval=3D [KNL] Set task-shuffle interval (s). Shuffling tasks allows some CPUs to go into dyntick-idle mode diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index f96ab98f8182f..405decec33677 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -111,6 +111,7 @@ torture_param(int, nocbs_nthreads, 0, "Number of NOCB t= oggle threads, 0 to disab torture_param(int, nocbs_toggle, 1000, "Time between toggling nocb state (= ms)"); torture_param(int, read_exit_delay, 13, "Delay between read-then-exit epis= odes (s)"); torture_param(int, read_exit_burst, 16, "# of read-then-exit bursts per ep= isode, zero to disable"); +torture_param(int, reader_flavor, 0x1, "Reader flavors to use, one per bit= ."); torture_param(int, shuffle_interval, 3, "Number of seconds between shuffle= s"); torture_param(int, shutdown_secs, 0, "Shutdown time (s), <=3D zero to disa= ble."); torture_param(int, stall_cpu, 0, "Stall duration (s), zero to disable."); @@ -644,10 +645,20 @@ static void srcu_get_gp_data(int *flags, unsigned lon= g *gp_seq) =20 static int srcu_torture_read_lock(void) { - if (cur_ops =3D=3D &srcud_ops) - return srcu_read_lock_nmisafe(srcu_ctlp); - else - return srcu_read_lock(srcu_ctlp); + int idx; + int ret =3D 0; + + if ((reader_flavor & 0x1) || !(reader_flavor & 0x7)) { + idx =3D srcu_read_lock(srcu_ctlp); + WARN_ON_ONCE(idx & ~0x1); + ret +=3D idx; + } + if (reader_flavor & 0x2) { + idx =3D srcu_read_lock_nmisafe(srcu_ctlp); + WARN_ON_ONCE(idx & ~0x1); + ret +=3D idx << 1; + } + return ret; } =20 static void @@ -671,10 +682,11 @@ srcu_read_delay(struct torture_random_state *rrsp, st= ruct rt_read_seg *rtrsp) =20 static void srcu_torture_read_unlock(int idx) { - if (cur_ops =3D=3D &srcud_ops) - srcu_read_unlock_nmisafe(srcu_ctlp, idx); - else - srcu_read_unlock(srcu_ctlp, idx); + WARN_ON_ONCE((reader_flavor && (idx & ~reader_flavor)) || (!reader_flavor= && (idx & ~0x1))); + if (reader_flavor & 0x2) + srcu_read_unlock_nmisafe(srcu_ctlp, (idx & 0x2) >> 1); + if ((reader_flavor & 0x1) || !(reader_flavor & 0x7)) + srcu_read_unlock(srcu_ctlp, idx & 0x1); } =20 static int torture_srcu_read_lock_held(void) @@ -2389,6 +2401,7 @@ rcu_torture_print_module_parms(struct rcu_torture_ops= *cur_ops, const char *tag) "n_barrier_cbs=3D%d " "onoff_interval=3D%d onoff_holdoff=3D%d " "read_exit_delay=3D%d read_exit_burst=3D%d " + "reader_flavor=3D%x " "nocbs_nthreads=3D%d nocbs_toggle=3D%d " "test_nmis=3D%d\n", torture_type, tag, nrealreaders, nfakewriters, @@ -2401,6 +2414,7 @@ rcu_torture_print_module_parms(struct rcu_torture_ops= *cur_ops, const char *tag) n_barrier_cbs, onoff_interval, onoff_holdoff, read_exit_delay, read_exit_burst, + reader_flavor, nocbs_nthreads, nocbs_toggle, test_nmis); } --=20 2.40.1 From nobody Wed Nov 27 06:37:06 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AB4DF1C8FC0; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; cv=none; b=dugbhNU29sR7hSMvj673a7Ci6eSw57XfyXe5WXv2pQcqpDiaxuMtqNoNNrP6PZkmw2vxcZ9GXSlfE4KzR0QqB6EU5SRikK7f9qYL1ydDu3+V4zA/AJgSHdg9kDBTu0Mh1BuCOnTRXs3yq1Q2sHwEu7UHan7PixAbmY2Yuzpga2g= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; c=relaxed/simple; bh=2/hu6Yi0XsmLS7jmPPcP2qqf4oo1mhmwzrHcI6b4xBA=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=fYYIzrkeYpcQCWnClG0PR/lbxvgUHKcURmr7xM8Eno9JplBloJa3okRmvJ5xQq8xABb5qDd4kGINDF/jNu4I++kiGt4B175cIkO7b8NKiiYGTvxZAznujH4zQDtq3FN0vu85WX11F8b/R7w93btnZr36oElzRJRdYujy34YbONQ= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=eZnA64R0; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="eZnA64R0" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 66F2EC4CECF; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728668373; bh=2/hu6Yi0XsmLS7jmPPcP2qqf4oo1mhmwzrHcI6b4xBA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eZnA64R0ZeQ681YG9A5oU06l2QqEKnA9DWhONKA/HCfSWdJQquJlN38/U4a7sD6I5 t8avRXal1UwdDUm1OCZ81a+KLhGFvpa6/W43n+lhi/mKJ47qygR04S6BikO/ufVZ/f xcpyNqEYgcPNuiS8n5FgHWF2eH57wBfJ8LHomzyiq1a3332GuKJmG1DmLayrut09jI 2oM9OWGQ2vSf+AB4viTowxKEcbidyA6sQDiw1TX0HOPzOU7A2T8oEwS0IurkiyS9Gy VrMrjbvRPQr2OLsUSDBAz2S6gYYEpnKMpmnE+7+IIrhRTwLjNSxqSDV9DneuFL+X/4 8dziQtQaHNg9w== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id B2BC0CE0F99; Fri, 11 Oct 2024 10:39:32 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH v2 rcu 10/13] rcutorture: Add srcu_read_lock_lite() support to rcutorture.reader_flavor Date: Fri, 11 Oct 2024 10:39:28 -0700 Message-Id: <20241011173931.2050422-10-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> References: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" This commit causes bit 0x4 of rcutorture.reader_flavor to select the new srcu_read_lock_lite() and srcu_read_unlock_lite() functions. Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- Documentation/admin-guide/kernel-parameters.txt | 4 ++-- kernel/rcu/rcutorture.c | 7 +++++++ 2 files changed, 9 insertions(+), 2 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentatio= n/admin-guide/kernel-parameters.txt index 52922727006fc..203ec51e41d48 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -5431,8 +5431,8 @@ If there is more than one bit set, the readers are entered from low-order bit up, and are exited in the opposite order. For SRCU, the - 0x1 bit is normal readers and the 0x2 bit is - for NMI-safe readers. + 0x1 bit is normal readers, 0x2 NMI-safe readers, + and 0x4 light-weight readers. =20 rcutorture.shuffle_interval=3D [KNL] Set task-shuffle interval (s). Shuffling tasks diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c index 405decec33677..a313cdcb0960f 100644 --- a/kernel/rcu/rcutorture.c +++ b/kernel/rcu/rcutorture.c @@ -658,6 +658,11 @@ static int srcu_torture_read_lock(void) WARN_ON_ONCE(idx & ~0x1); ret +=3D idx << 1; } + if (reader_flavor & 0x4) { + idx =3D srcu_read_lock_lite(srcu_ctlp); + WARN_ON_ONCE(idx & ~0x1); + ret +=3D idx << 2; + } return ret; } =20 @@ -683,6 +688,8 @@ srcu_read_delay(struct torture_random_state *rrsp, stru= ct rt_read_seg *rtrsp) static void srcu_torture_read_unlock(int idx) { WARN_ON_ONCE((reader_flavor && (idx & ~reader_flavor)) || (!reader_flavor= && (idx & ~0x1))); + if (reader_flavor & 0x4) + srcu_read_unlock_lite(srcu_ctlp, (idx & 0x4) >> 2); if (reader_flavor & 0x2) srcu_read_unlock_nmisafe(srcu_ctlp, (idx & 0x2) >> 1); if ((reader_flavor & 0x1) || !(reader_flavor & 0x7)) --=20 2.40.1 From nobody Wed Nov 27 06:37:06 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B25131C9B91; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; cv=none; b=t68zviXqrdflRVzOoFACZzojfsctQ4vUJjQHBW3uqUTZMI+q3PXEQeYy4DZCNYCyKBOK9nhYvFiG66+fgQlFx70CvZQjGZDjUHmAEC39zIGZKymPePHrWLZa3PRj7jXJsj9OeqLJ6jzCqpiqa/Z4lpo24ub2QvULq3LYxFfoKwA= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; c=relaxed/simple; bh=aRxkj03S73hF0jV8gryZajtKN0A7DA6aTKR8Jq/1sgk=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=nP1zZAcRLY38qAS384LKbavXE5AIY2hi+hn5Dt5TPafzN43pCBZAFTSRg5sb0FwUWsIEid7uCl1ZVVbtdO9YxQrg0fWTROYS6m1ixfwgouVeSHjVAvWMJK5hrdFoJ2JwT+fOs4Wo+G9jJBp4XAxo/WiQoFKpAxFsRyp68OBO/0c= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=pJ/ezhwt; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="pJ/ezhwt" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6BB7FC4CEE2; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728668373; bh=aRxkj03S73hF0jV8gryZajtKN0A7DA6aTKR8Jq/1sgk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=pJ/ezhwtdqid/ZsVPuQol1wyZCHB8dGpZSSm5GCtXCeT6tRoERkz7sQMUv95nkYzQ WRjbcGAoFmhmsndhDMB6l2/E2p/fOChpWHSB5yRxKqOjo+YebMr3kPfAR7KLCRfcDi ha+76hznaYRAG7sSc7/Y/UspbQsGiW8w8crbNiv1AGG0LOiv3NcocQTSISHYP2Atzl UnIfJXcjw9V2D16HLeXAbT9p5lY197sR58QaNueOv9ZE4yrOGoJYkZ1jzyTAjnzMrt oZRqAKdXd9Jm7S2wIQB3AOEGoFR85LHHQ9qMCKkePc6dHseq40gJx/RCHXJBMnrazE QpuJQ+rZdpT2w== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id B5BB9CE0F9C; Fri, 11 Oct 2024 10:39:32 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH v2 rcu 11/13] rcutorture: Add light-weight SRCU scenario Date: Fri, 11 Oct 2024 10:39:29 -0700 Message-Id: <20241011173931.2050422-11-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> References: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" This commit adds an rcutorture scenario that tests light-weight SRCU readers. While in the area, it adjusts the size of the TREE10 scenario. Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- tools/testing/selftests/rcutorture/configs/rcu/CFLIST | 1 + tools/testing/selftests/rcutorture/configs/rcu/SRCU-L | 10 ++++++++++ .../selftests/rcutorture/configs/rcu/SRCU-L.boot | 3 +++ .../selftests/rcutorture/configs/rcu/SRCU-N.boot | 1 + tools/testing/selftests/rcutorture/configs/rcu/TREE10 | 2 +- 5 files changed, 16 insertions(+), 1 deletion(-) create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/SRCU-L create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/SRCU-L.b= oot diff --git a/tools/testing/selftests/rcutorture/configs/rcu/CFLIST b/tools/= testing/selftests/rcutorture/configs/rcu/CFLIST index 98b6175e5aa09..45f572570a8c3 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/CFLIST +++ b/tools/testing/selftests/rcutorture/configs/rcu/CFLIST @@ -5,6 +5,7 @@ TREE04 TREE05 TREE07 TREE09 +SRCU-L SRCU-N SRCU-P SRCU-T diff --git a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-L b/tools/= testing/selftests/rcutorture/configs/rcu/SRCU-L new file mode 100644 index 0000000000000..3b4fa8dbef8a9 --- /dev/null +++ b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-L @@ -0,0 +1,10 @@ +CONFIG_RCU_TRACE=3Dn +CONFIG_SMP=3Dy +CONFIG_NR_CPUS=3D6 +CONFIG_HOTPLUG_CPU=3Dy +CONFIG_PREEMPT_NONE=3Dy +CONFIG_PREEMPT_VOLUNTARY=3Dn +CONFIG_PREEMPT=3Dn +#CHECK#CONFIG_RCU_EXPERT=3Dn +CONFIG_KPROBES=3Dn +CONFIG_FTRACE=3Dn diff --git a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-L.boot b/t= ools/testing/selftests/rcutorture/configs/rcu/SRCU-L.boot new file mode 100644 index 0000000000000..0207b3138c5be --- /dev/null +++ b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-L.boot @@ -0,0 +1,3 @@ +rcutorture.torture_type=3Dsrcu +rcutorture.reader_flavor=3D0x4 +rcutorture.fwd_progress=3D3 diff --git a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-N.boot b/t= ools/testing/selftests/rcutorture/configs/rcu/SRCU-N.boot index ce0694fd9b929..b54cf87dc1103 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/SRCU-N.boot +++ b/tools/testing/selftests/rcutorture/configs/rcu/SRCU-N.boot @@ -1,2 +1,3 @@ rcutorture.torture_type=3Dsrcu +rcutorture.reader_flavor=3D0x2 rcutorture.fwd_progress=3D3 diff --git a/tools/testing/selftests/rcutorture/configs/rcu/TREE10 b/tools/= testing/selftests/rcutorture/configs/rcu/TREE10 index a323d8948b7cf..759ee51d3ddc6 100644 --- a/tools/testing/selftests/rcutorture/configs/rcu/TREE10 +++ b/tools/testing/selftests/rcutorture/configs/rcu/TREE10 @@ -1,5 +1,5 @@ CONFIG_SMP=3Dy -CONFIG_NR_CPUS=3D56 +CONFIG_NR_CPUS=3D74 CONFIG_PREEMPT_NONE=3Dy CONFIG_PREEMPT_VOLUNTARY=3Dn CONFIG_PREEMPT=3Dn --=20 2.40.1 From nobody Wed Nov 27 06:37:06 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B6CC31C9B97; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; cv=none; b=uguEun9STXNTjAQhmkXPao6ZLWBy3OuqC4AmHGQoUT/l7ORyr17sEACR4hpzHqVlMIOiPV53Tj93s3L6Pwy5xVFkaWBnD43jmGjMDeek9T/+kFAua2EqBpczlJNLAXs58B31q8iC+QYSfbtvqGQ6jwpCA02l0tRGVyj3qqstcts= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; c=relaxed/simple; bh=ShAY23PXWJnTwN9m3aELbGSryO452AQIXFVffiHUjJ8=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=qJz9TsROkCFsVzCyPLFJ9Ctc0knsHok5Iyx+5fVAv1AJ2QTMlMTRVWfv8rOH9j9O8JQqAfmqSgl+V/ghrc0npzDtCYyvTrhy+Xhx8lt27V0A2rNUwWFQU/vLiTQy1KATml8eA7UnTgEX06Sfkc6zBVd4+E47D/WJvlQEwKotGRk= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=qZ2hdvVT; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="qZ2hdvVT" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6E0D5C4CEDF; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728668373; bh=ShAY23PXWJnTwN9m3aELbGSryO452AQIXFVffiHUjJ8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qZ2hdvVT0seSG7P9xAp+Nfp1Cy6Rc+ziKChMFejj4pIc0mrXe0g5jULUHzjt7mlPP rRQu1Ze3UPmPQ+Se3f27pjFL99b7v0K/yD63UbKadhzN0/BNM6buzq5kUXqEg/TJPw rdxgnSSTZYn11tlHhsYaQY7+D9wWKOs9NpCuMIzro+u6RWslj7KMZIgfzLgLmHm+i0 bhBfQiBc6Bn0iFHApB8WK3DfmTJWyPvQQBGIpXeXa3Pp1CtYpAlnJzljPvuPiu1+ff 4fz3hbFScFXgVVBfHdqH927XZnTNjX10qfVbbmVjV/1PKCpXiUUC15IBh26eyC09/e 5oTCbLg0JfanA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id B8907CE0FA0; Fri, 11 Oct 2024 10:39:32 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Alexei Starovoitov , Andrii Nakryiko , Peter Zijlstra , Kent Overstreet , bpf@vger.kernel.org Subject: [PATCH v2 rcu 12/13] refscale: Add srcu_read_lock_lite() support using "srcu-lite" Date: Fri, 11 Oct 2024 10:39:30 -0700 Message-Id: <20241011173931.2050422-12-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> References: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" This commit creates a new srcu-lite option for the refscale.scale_type module parameter that selects srcu_read_lock_lite() and srcu_read_unlock_lite(). Signed-off-by: Paul E. McKenney Cc: Alexei Starovoitov Cc: Andrii Nakryiko Cc: Peter Zijlstra Cc: Kent Overstreet Cc: --- kernel/rcu/refscale.c | 51 +++++++++++++++++++++++++++++++++---------- 1 file changed, 40 insertions(+), 11 deletions(-) diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c index 0db9db73f57f2..09ee27ced2a78 100644 --- a/kernel/rcu/refscale.c +++ b/kernel/rcu/refscale.c @@ -212,6 +212,36 @@ static const struct ref_scale_ops srcu_ops =3D { .name =3D "srcu" }; =20 +static void srcu_lite_ref_scale_read_section(const int nloops) +{ + int i; + int idx; + + for (i =3D nloops; i >=3D 0; i--) { + idx =3D srcu_read_lock_lite(srcu_ctlp); + srcu_read_unlock_lite(srcu_ctlp, idx); + } +} + +static void srcu_lite_ref_scale_delay_section(const int nloops, const int = udl, const int ndl) +{ + int i; + int idx; + + for (i =3D nloops; i >=3D 0; i--) { + idx =3D srcu_read_lock_lite(srcu_ctlp); + un_delay(udl, ndl); + srcu_read_unlock_lite(srcu_ctlp, idx); + } +} + +static const struct ref_scale_ops srcu_lite_ops =3D { + .init =3D rcu_sync_scale_init, + .readsection =3D srcu_lite_ref_scale_read_section, + .delaysection =3D srcu_lite_ref_scale_delay_section, + .name =3D "srcu-lite" +}; + #ifdef CONFIG_TASKS_RCU =20 // Definitions for RCU Tasks ref scale testing: Empty read markers. @@ -1082,27 +1112,26 @@ ref_scale_init(void) long i; int firsterr =3D 0; static const struct ref_scale_ops *scale_ops[] =3D { - &rcu_ops, &srcu_ops, RCU_TRACE_OPS RCU_TASKS_OPS &refcnt_ops, &rwlock_op= s, - &rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_ops, &clock_ops, &jiffies_= ops, - &typesafe_ref_ops, &typesafe_lock_ops, &typesafe_seqlock_ops, + &rcu_ops, &srcu_ops, &srcu_lite_ops, RCU_TRACE_OPS RCU_TASKS_OPS + &refcnt_ops, &rwlock_ops, &rwsem_ops, &lock_ops, &lock_irq_ops, &acqrel_= ops, + &clock_ops, &jiffies_ops, &typesafe_ref_ops, &typesafe_lock_ops, + &typesafe_seqlock_ops, }; =20 if (!torture_init_begin(scale_type, verbose)) return -EBUSY; =20 for (i =3D 0; i < ARRAY_SIZE(scale_ops); i++) { - cur_ops =3D scale_ops[i]; - if (strcmp(scale_type, cur_ops->name) =3D=3D 0) + cur_ops =3D scale_ops[i]; if (strcmp(scale_type, + cur_ops->name) =3D=3D 0) break; } if (i =3D=3D ARRAY_SIZE(scale_ops)) { - pr_alert("rcu-scale: invalid scale type: \"%s\"\n", scale_type); - pr_alert("rcu-scale types:"); - for (i =3D 0; i < ARRAY_SIZE(scale_ops); i++) + pr_alert("rcu-scale: invalid scale type: \"%s\"\n", + scale_type); pr_alert("rcu-scale types:"); for (i =3D 0; + i < ARRAY_SIZE(scale_ops); i++) pr_cont(" %s", scale_ops[i]->name); - pr_cont("\n"); - firsterr =3D -EINVAL; - cur_ops =3D NULL; + pr_cont("\n"); firsterr =3D -EINVAL; cur_ops =3D NULL; goto unwind; } if (cur_ops->init) --=20 2.40.1 From nobody Wed Nov 27 06:37:06 2024 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B0A401C9B81; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; cv=none; b=ASMOgbtSoDSqzZEkBs8nPaAhnt1DI+q5jFr3NYvkdUaHgX2i5eJrOxZNuf1YU8Bhls0y3b/UBjZ4btbRRp2fGDk9cIVEN2r7VEAs0R/2Tdw8sDo4b/TyrIbWwwK+JJtoAY3OEWWJCQMsUiIE+G0V4dMDV7WOgN3ocBLawRNYatk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728668373; c=relaxed/simple; bh=VNnp30uwfjWqvy4NVapgi+LtAjMkx2x6Xh+V0F6TxJc=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=f1xRhGuIcgh966WoucX0ZuIksybc6ju3zxRVlOnS+qw9IdpRlPZ5qvKiHf9Bk5hpZF0Bc+4dJVtAAhenn6LwOKI1qk0pzr0awyQzrDCoky7wCKO8QUJ+NMhdhjw9UDIN+fS0HI0t91W9XnDfP+dwF4Txq2CeGfdL3jBIPMDzJ4k= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=kJDthcDV; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="kJDthcDV" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7552BC4CEE9; Fri, 11 Oct 2024 17:39:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728668373; bh=VNnp30uwfjWqvy4NVapgi+LtAjMkx2x6Xh+V0F6TxJc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=kJDthcDVPT+fOdB96517oOtcGm0m3SXUyyyWEK2FgWFZ8xjiGJthcTa39kt9LGO8M PE+/v8ddA1+4Q6452OBCFcbS9SzxKN0UD5TaNF+Vy9JRFSdYlOxQGhIbVL66kWVP/E mV99ayR/nKSFjbdiBvpbPbS/jek1OgZyIfMK3hte6axmB6ouN2HKnwjx8aEQq4weo7 sqYkJvKkkN5xHtfaOEfm2IDIX7vsJvUfrPu3wRZabIyMNJhl/EDsmJHesuxFQsj7tB 4BPBSReKsUbjEKOPmvAI8LxHjooCOTgmBCffS/jR0je7iohCqid5Ay6pTrKlDN1CF8 8SpwPYInwxGNA== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id BADCFCE0FEF; Fri, 11 Oct 2024 10:39:32 -0700 (PDT) From: "Paul E. McKenney" To: frederic@kernel.org, rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Andrii Nakryiko Subject: [PATCH v2 rcu 13/13] srcu: Improve srcu_read_lock_lite() kernel-doc comment Date: Fri, 11 Oct 2024 10:39:31 -0700 Message-Id: <20241011173931.2050422-13-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> References: <3b82ac1a-8786-4a27-8eff-ecc67b50dfb6@paulmck-laptop> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Where RCU is watching is where it is OK to invoke rcu_read_lock(). Reported-by: Andrii Nakryiko Signed-off-by: Paul E. McKenney Acked-by: Andrii Nakryiko --- include/linux/srcu.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 4ba96e2cfa405..bab1dae3f69e6 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -270,7 +270,8 @@ static inline int srcu_read_lock(struct srcu_struct *ss= p) __acquires(ssp) * synchronize_rcu_expedited(), IPIs and all. * * Note that srcu_read_lock_lite() can be invoked only from those contexts - * where RCU is watching. Otherwise, lockdep will complain. + * where RCU is watching, that is, from contexts where it would be legal + * to invoke rcu_read_lock(). Otherwise, lockdep will complain. */ static inline int srcu_read_lock_lite(struct srcu_struct *ssp) __acquires(= ssp) { --=20 2.40.1