From mboxrd@z Thu Jan 1 00:00:00 1970 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 441DD224F1; Sun, 24 Mar 2024 17:07:17 +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=1711300037; cv=none; b=QcATRpcoqhWYDYX7tlcB12AEHDE9WqBGjT4SuvGz6eCJxqwxSdRSPv3YWVvOxOrB1MjQhhtwVeMmeB1uRwrdLA8MDy+ASrqwgcFvWgiy4Ar09vJQo2WaRQ9xmdvMXr/+hsnfzTKfr/8LqaPcNC+9ZP/PykSfaq/tLHRlfTBKbko= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1711300037; c=relaxed/simple; bh=5A4YIkHqVwwTm1pf2aHh/AAntir5ZY/Uchu5RnKY8fw=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Ct8yUdkwlwIr6lZbSvz7PBEFhU+jsC1X2kkfGUA8qt8r+7daMvHByehL4YHpCgtQxz8hiKd0f9LlmE6laPgbyKiBpilysLHGt7aYfbzlQXV3lHYOG5eDDt9+AT0keMjwwqBktoO7vOrLSmaIZF5jfc1Xl+po/nIGbdw5N7hmi/8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=k8pa1pjN; 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="k8pa1pjN" Received: by smtp.kernel.org (Postfix) with ESMTPSA id CF1E6C433A6; Sun, 24 Mar 2024 17:07:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1711300037; bh=5A4YIkHqVwwTm1pf2aHh/AAntir5ZY/Uchu5RnKY8fw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=k8pa1pjNVVjd4x5fjrYImoEqu26NhpH5tQXv/6sdWPydFdv9Al4nwQ6wRxh111sDU C+A1SE0ErHewITe7CQy/VV5xkizfSKY9eEx1JaV2i0xJRmxJh5QJskLoPcixR8NJBE 2mFkOhh+XZjUaGDZDp2/1weVNploOtxKqn7OsQ0q1LVYAZ2CcwyGobBZXnIP92nIcu c5gaKFKiICfBT4o7uXasY03D6IhEMi+3q+simmOgTL4vuiwSfbisiReDkq8K1YbWR5 9BUa4vxLQsFIDWXkngPQj8X7iBI5CzOXZ+hev5d/1ZAxcjbmTCzZIcmkgDkA3XYr6p NyTCb2JS0NVdw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: "Paul E. McKenney" , Chen Zhongjin , Yang Jihong , Frederic Weisbecker , Boqun Feng , Sasha Levin , quic_neeraju@quicinc.com, joel@joelfernandes.org, josh@joshtriplett.org, rcu@vger.kernel.org Subject: [PATCH AUTOSEL 6.1 4/7] rcu-tasks: Maintain lists to eliminate RCU-tasks/do_exit() deadlocks Date: Sun, 24 Mar 2024 13:07:04 -0400 Message-ID: <20240324170709.546465-4-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240324170709.546465-1-sashal@kernel.org> References: <20240324170709.546465-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 6.1.82 Content-Transfer-Encoding: 8bit From: "Paul E. McKenney" [ Upstream commit 6b70399f9ef3809f6e308fd99dd78b072c1bd05c ] This commit continues the elimination of deadlocks involving do_exit() and RCU tasks by causing exit_tasks_rcu_start() to add the current task to a per-CPU list and causing exit_tasks_rcu_stop() to remove the current task from whatever list it is on. These lists will be used to track tasks that are exiting, while still accounting for any RCU-tasks quiescent states that these tasks pass though. [ paulmck: Apply Frederic Weisbecker feedback. ] Link: https://lore.kernel.org/all/20240118021842.290665-1-chenzhongjin@huawei.com/ Reported-by: Chen Zhongjin Reported-by: Yang Jihong Signed-off-by: Paul E. McKenney Tested-by: Yang Jihong Tested-by: Chen Zhongjin Reviewed-by: Frederic Weisbecker Signed-off-by: Boqun Feng Signed-off-by: Sasha Levin --- kernel/rcu/tasks.h | 43 +++++++++++++++++++++++++++++++++---------- 1 file changed, 33 insertions(+), 10 deletions(-) diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h index 919c22698569e..76ad0bc2b3312 100644 --- a/kernel/rcu/tasks.h +++ b/kernel/rcu/tasks.h @@ -1014,25 +1014,48 @@ EXPORT_SYMBOL_GPL(show_rcu_tasks_classic_gp_kthread); #endif // !defined(CONFIG_TINY_RCU) /* - * Contribute to protect against tasklist scan blind spot while the - * task is exiting and may be removed from the tasklist. See - * corresponding synchronize_srcu() for further details. + * Protect against tasklist scan blind spot while the task is exiting and + * may be removed from the tasklist. Do this by adding the task to yet + * another list. + * + * Note that the task will remove itself from this list, so there is no + * need for get_task_struct(), except in the case where rcu_tasks_pertask() + * adds it to the holdout list, in which case rcu_tasks_pertask() supplies + * the needed get_task_struct(). */ -void exit_tasks_rcu_start(void) __acquires(&tasks_rcu_exit_srcu) +void exit_tasks_rcu_start(void) { - current->rcu_tasks_idx = __srcu_read_lock(&tasks_rcu_exit_srcu); + unsigned long flags; + struct rcu_tasks_percpu *rtpcp; + struct task_struct *t = current; + + WARN_ON_ONCE(!list_empty(&t->rcu_tasks_exit_list)); + preempt_disable(); + rtpcp = this_cpu_ptr(rcu_tasks.rtpcpu); + t->rcu_tasks_exit_cpu = smp_processor_id(); + raw_spin_lock_irqsave_rcu_node(rtpcp, flags); + if (!rtpcp->rtp_exit_list.next) + INIT_LIST_HEAD(&rtpcp->rtp_exit_list); + list_add(&t->rcu_tasks_exit_list, &rtpcp->rtp_exit_list); + raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags); + preempt_enable(); } /* - * Contribute to protect against tasklist scan blind spot while the - * task is exiting and may be removed from the tasklist. See - * corresponding synchronize_srcu() for further details. + * Remove the task from the "yet another list" because do_exit() is now + * non-preemptible, allowing synchronize_rcu() to wait beyond this point. */ -void exit_tasks_rcu_stop(void) __releases(&tasks_rcu_exit_srcu) +void exit_tasks_rcu_stop(void) { + unsigned long flags; + struct rcu_tasks_percpu *rtpcp; struct task_struct *t = current; - __srcu_read_unlock(&tasks_rcu_exit_srcu, t->rcu_tasks_idx); + WARN_ON_ONCE(list_empty(&t->rcu_tasks_exit_list)); + rtpcp = per_cpu_ptr(rcu_tasks.rtpcpu, t->rcu_tasks_exit_cpu); + raw_spin_lock_irqsave_rcu_node(rtpcp, flags); + list_del_init(&t->rcu_tasks_exit_list); + raw_spin_unlock_irqrestore_rcu_node(rtpcp, flags); } /* -- 2.43.0