From nobody Fri Dec 19 16:03:30 2025 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 C672734AB1C; Wed, 5 Nov 2025 20:32:20 +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=1762374740; cv=none; b=RD7PJ3LLlsWJr6dG0YKz7Mf1P5XBppJVYxAUNfURCGxISf/q8KYYSeKFdAp++HmxR4BvlDnjwP/RZLKlsknL9lljIKllWoIB8j4XmwiiSjjNGX4j6S6y9q/UeOdbmnvEv6I0jIzo/nQd0DlRjxGjsfWDem5KRdYNpylaU6601p0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1762374740; c=relaxed/simple; bh=MZmvN2dS91ATVvwCaKa51PWDnZiCJGVXmJf2Q3doHC0=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=hln0L4p7r1bqWk/0D64Ki07vEvAQkYxTVvC92Cm8DbHGz0A7zAVWedAJlvYAl+Esvr70cvREgj86k70w8vQ5HGcC722JSCHgimo1ECAg+AumoKELxkyJ1CzmNCWXAZ0pFmHPW8KrlcHKUUPevfcuRbYXB+fyrrBLcRlLeG7OnkI= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=IQgi5fxR; 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="IQgi5fxR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5ADDFC4AF0C; Wed, 5 Nov 2025 20:32:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1762374740; bh=MZmvN2dS91ATVvwCaKa51PWDnZiCJGVXmJf2Q3doHC0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IQgi5fxR5PnrnjE9tykMd/2rpgOQ3qY2iIK4XVLA2X5khMkAPigAY2KTHP4pDomK6 I0tUH7i9ex4SxbivNVt/0mK2uGBWmD6weNBXpMFi3qESqGpjgrv7cPaYXcWqPHKs2o QYo55dC6FmT5uVB50KueuWZJCZcm3JriQ8FxecR0LOso0bdDMsIZ/nD450AtJPV5VM +cdGmurTFNDxR2u9hJWqCCoMi0cY1aC7oKCsFKmTE04XbHf2GnghHNgCTp5Tjm6b7G nGl5lDwYvi97C7/tCNIO+b9emJYX+x9qTUHj/0NwNfngPxadTDMLV3rkBpNrtMMJ9g /wIhNv5IbIsgQ== Received: by paulmck-ThinkPad-P17-Gen-1.home (Postfix, from userid 1000) id 9950ACE0F65; Wed, 5 Nov 2025 12:32:18 -0800 (PST) From: "Paul E. McKenney" To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, kernel-team@meta.com, rostedt@goodmis.org, "Paul E. McKenney" , Mathieu Desnoyers , Sebastian Andrzej Siewior , bpf@vger.kernel.org Subject: [PATCH v2 08/16] srcu: Make SRCU-fast readers enforce use of SRCU-fast definition/init Date: Wed, 5 Nov 2025 12:32:08 -0800 Message-Id: <20251105203216.2701005-8-paulmck@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: References: 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 makes CONFIG_PROVE_RCU=3Dy kernels enforce the new rule that srcu_struct structures that are passed to srcu_read_lock_fast() and other SRCU-fast read-side markers be either initialized with init_srcu_struct_fast() on the one hand or defined with DEFINE_SRCU_FAST() or DEFINE_STATIC_SRCU_FAST() on the other. This eliminates the read-side test that was formerly included in srcu_read_lock_fast() and friends, speeding these primitives up by about 25% (admittedly only about half of a nanosecond, but when tracing on fastpaths...) Signed-off-by: Paul E. McKenney Cc: Mathieu Desnoyers Cc: Steven Rostedt Cc: Sebastian Andrzej Siewior Cc: --- include/linux/srcu.h | 6 +++--- include/linux/srcutiny.h | 1 - include/linux/srcutree.h | 16 +--------------- 3 files changed, 4 insertions(+), 19 deletions(-) diff --git a/include/linux/srcu.h b/include/linux/srcu.h index 2982b5a6930f..41e27c1d917d 100644 --- a/include/linux/srcu.h +++ b/include/linux/srcu.h @@ -297,7 +297,7 @@ static inline struct srcu_ctr __percpu *srcu_read_lock_= fast(struct srcu_struct * struct srcu_ctr __percpu *retval; =20 RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_read_lock= _fast()."); - srcu_check_read_flavor_force(ssp, SRCU_READ_FLAVOR_FAST); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_FAST); retval =3D __srcu_read_lock_fast(ssp); rcu_try_lock_acquire(&ssp->dep_map); return retval; @@ -312,7 +312,7 @@ static inline struct srcu_ctr __percpu *srcu_read_lock_= fast_notrace(struct srcu_ { struct srcu_ctr __percpu *retval; =20 - srcu_check_read_flavor_force(ssp, SRCU_READ_FLAVOR_FAST); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_FAST); retval =3D __srcu_read_lock_fast(ssp); return retval; } @@ -333,7 +333,7 @@ static inline struct srcu_ctr __percpu *srcu_down_read_= fast(struct srcu_struct * { WARN_ON_ONCE(IS_ENABLED(CONFIG_PROVE_RCU) && in_nmi()); RCU_LOCKDEP_WARN(!rcu_is_watching(), "RCU must be watching srcu_down_read= _fast()."); - srcu_check_read_flavor_force(ssp, SRCU_READ_FLAVOR_FAST); + srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_FAST); return __srcu_read_lock_fast(ssp); } =20 diff --git a/include/linux/srcutiny.h b/include/linux/srcutiny.h index 92e6ab53398f..1ecc3393fb26 100644 --- a/include/linux/srcutiny.h +++ b/include/linux/srcutiny.h @@ -112,7 +112,6 @@ static inline void srcu_barrier(struct srcu_struct *ssp) =20 static inline void srcu_expedite_current(struct srcu_struct *ssp) { } #define srcu_check_read_flavor(ssp, read_flavor) do { } while (0) -#define srcu_check_read_flavor_force(ssp, read_flavor) do { } while (0) =20 /* Defined here to avoid size increase for non-torture kernels. */ static inline void srcu_torture_stats_print(struct srcu_struct *ssp, diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h index 7ff4a11bc5a3..6080a9094618 100644 --- a/include/linux/srcutree.h +++ b/include/linux/srcutree.h @@ -307,21 +307,7 @@ __srcu_read_unlock_fast(struct srcu_struct *ssp, struc= t srcu_ctr __percpu *scp) =20 void __srcu_check_read_flavor(struct srcu_struct *ssp, int read_flavor); =20 -// Record reader usage even for CONFIG_PROVE_RCU=3Dn kernels. This is -// needed only for flavors that require grace-period smp_mb() calls to be -// promoted to synchronize_rcu(). -static inline void srcu_check_read_flavor_force(struct srcu_struct *ssp, i= nt read_flavor) -{ - struct srcu_data *sdp =3D raw_cpu_ptr(ssp->sda); - - if (likely(READ_ONCE(sdp->srcu_reader_flavor) & read_flavor)) - return; - - // Note that the cmpxchg() in __srcu_check_read_flavor() is fully ordered. - __srcu_check_read_flavor(ssp, read_flavor); -} - -// Record non-_lite() usage only for CONFIG_PROVE_RCU=3Dy kernels. +// Record SRCU-reader usage type only for CONFIG_PROVE_RCU=3Dy kernels. static inline void srcu_check_read_flavor(struct srcu_struct *ssp, int rea= d_flavor) { if (IS_ENABLED(CONFIG_PROVE_RCU)) --=20 2.40.1