From nobody Wed Nov 27 16:31:50 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 278D01A2C19; Wed, 9 Oct 2024 12:52:26 +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=1728478347; cv=none; b=m7rQj2jeSCQJ+8zcoRH3uqxW7k8FpEh51MehQCnEExYhpk8HJjF5F4/QPx+1lwrW/k/bjbsffFDmK9tw8E9r8TMIUMFuIdWN4yLtXVSsKXJ3ikoEddQX/3M7TtWWYu38Z7XnW9KfVOPOZKr8pZ5WihvMv8S/VZrSDEggAjvA5Mo= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1728478347; c=relaxed/simple; bh=lOXgRfOyLIl7elkNZsxeg0qekVV+z+V29DqLUPqFN78=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Wkanq1kYIY1cQHh5qkw7+5Qxmk0w3I8yCQhumXfeg73wA4vsE1d4VVc7Gr2YcbggtRy7ZayO+vFpsd+Hr5SJdna/Lqze3S8g4esPom1uBE1l0KiGi8MHnS4YRXcQoN9cYOgrAspt63LuVngb0xSQcMsKfGN+jXAvU8xl/Nw7gpg= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=K2ZxVGxf; 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="K2ZxVGxf" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A9566C4CEC5; Wed, 9 Oct 2024 12:52:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1728478346; bh=lOXgRfOyLIl7elkNZsxeg0qekVV+z+V29DqLUPqFN78=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=K2ZxVGxfr/4AK7Agl9MI+e69zrPCZb4KtzRhkDgzTrYKQ3K5Z1h9lZNmmfZx08Feo Vm49v6S2GgwaMl/SHf9zmG218tjoeJiodloI8duuCmI2Z55Lj00eZCl6L4w5hD3eMO /wEzKBGJmkg5vCNpvJN2yZY6UG4yOYcAfr0WJl7q9FzwBP2XDNRK2jly2PU0Ewfu8E GY/ss0KIeBs1We3lEfNwkuiaRLUEg6axGD+kSNsBwQyKBhG9vEum7C8iQcUTPrjA81 Klhth8uZ+zPjjBQeewcRFR/la0H2KZxtXjV1USkbXZyhtpuoLSgeWME8epe893eLj2 AbXNuCDN62hkw== From: neeraj.upadhyay@kernel.org To: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org, paulmck@kernel.org, joel@joelfernandes.org, frederic@kernel.org, boqun.feng@gmail.com, urezki@gmail.com, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, qiang.zhang1211@gmail.com, peterz@infradead.org, neeraj.upadhyay@amd.com, Neeraj Upadhyay Subject: [PATCH v2 09/10] context_tracking: Invoke RCU-tasks enter/exit for NMI context Date: Wed, 9 Oct 2024 18:21:26 +0530 Message-Id: <20241009125127.18902-10-neeraj.upadhyay@kernel.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20241009125127.18902-1-neeraj.upadhyay@kernel.org> References: <20241009125127.18902-1-neeraj.upadhyay@kernel.org> 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" From: Neeraj Upadhyay rcu_task_enter() and rcu_task_exit() are not called on NMI entry and exit. So, Tasks-RCU-Rude grace period wait is required to ensure that NMI handlers have entered/exited into Tasks-RCU eqs. For architectures which do not require Tasks-RCU-Rude (as the code sections where RCU is not watching are marked as noinstr), when those architectures switch to not using Tasks-RCU-Rude, NMI handlers task exit to eqs will need to be handled correctly for Tasks-RCU holdout tasks running on nohz_full CPUs. As it is safe to call these two functions from NMI context, remove the in_nmi() check. This ensures that RCU-tasks entry/exit is marked correctly for NMI handlers. With this check removed, all callers of ct_kernel_exit_state() and ct_kernel_enter_state() now also call rcu_task_exit() and rcu_task_enter() respectively. So, fold rcu_task_exit() and rcu_task_entry() calls into ct_kernel_exit_state() and ct_kernel_enter_state(). Reported-by: Frederic Weisbecker Suggested-by: Frederic Weisbecker Suggested-by: "Paul E. McKenney" Reviewed-by: Paul E. McKenney Signed-off-by: Neeraj Upadhyay --- kernel/context_tracking.c | 11 +++-------- 1 file changed, 3 insertions(+), 8 deletions(-) diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c index 938c48952d26..85ced563af23 100644 --- a/kernel/context_tracking.c +++ b/kernel/context_tracking.c @@ -91,6 +91,7 @@ static noinstr void ct_kernel_exit_state(int offset) seq =3D ct_state_inc(offset); // RCU is no longer watching. Better be in extended quiescent state! WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && (seq & CT_RCU_WATCHING)); + rcu_task_exit(); } =20 /* @@ -102,6 +103,8 @@ static noinstr void ct_kernel_enter_state(int offset) { int seq; =20 + rcu_task_enter(); + /* * CPUs seeing atomic_add_return() must see prior idle sojourns, * and we also must force ordering with the next RCU read-side @@ -149,7 +152,6 @@ static void noinstr ct_kernel_exit(bool user, int offse= t) // RCU is watching here ... ct_kernel_exit_state(offset); // ... but is no longer watching here. - rcu_task_exit(); } =20 /* @@ -173,7 +175,6 @@ static void noinstr ct_kernel_enter(bool user, int offs= et) ct->nesting++; return; } - rcu_task_enter(); // RCU is not watching here ... ct_kernel_enter_state(offset); // ... but is watching here. @@ -238,9 +239,6 @@ void noinstr ct_nmi_exit(void) // RCU is watching here ... ct_kernel_exit_state(CT_RCU_WATCHING); // ... but is no longer watching here. - - if (!in_nmi()) - rcu_task_exit(); } =20 /** @@ -273,9 +271,6 @@ void noinstr ct_nmi_enter(void) */ if (!rcu_is_watching_curr_cpu()) { =20 - if (!in_nmi()) - rcu_task_enter(); - // RCU is not watching here ... ct_kernel_enter_state(CT_RCU_WATCHING); // ... but is watching here. --=20 2.40.1