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 06C1311C83 for ; Mon, 28 Aug 2023 10:45:43 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A79CC433C7; Mon, 28 Aug 2023 10:45:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1693219542; bh=MWghyhnyl92tvQoALg4AsuxMi9fq1qcrzsxk0imtp+E=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=iwj09xUGplHwL3lfo8SbjUi4bMq3gnqxPi2C+a3v0kWmKui9FJKgkZvkakohfQ5G7 dv6d5DzKLuBbEvkYkizPFJIdOV179HLqRK9yVASqkVEpoBMWzdinx1IlKXxwIvnxUJ HC6vf4GGvrfEECubNWSnMXWoUwtuabWTBr+ZPfXg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Paul McKenney , Frederic Weisbecker , Zhouyi Zhou , "Joel Fernandes (Google)" , Davidlohr Bueso Subject: [PATCH 5.15 73/89] torture: Fix hang during kthread shutdown phase Date: Mon, 28 Aug 2023 12:14:14 +0200 Message-ID: <20230828101152.657057854@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20230828101150.163430842@linuxfoundation.org> References: <20230828101150.163430842@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 5.15-stable review patch. If anyone has any objections, please let me know. ------------------ From: Joel Fernandes (Google) commit d52d3a2bf408ff86f3a79560b5cce80efb340239 upstream. During rcutorture shutdown, the rcu_torture_cleanup() function calls torture_cleanup_begin(), which sets the fullstop global variable to FULLSTOP_RMMOD. This causes the rcutorture threads for readers and fakewriters to exit all of their "while" loops and start shutting down. They then call torture_kthread_stopping(), which in turn waits for kthread_stop() to be called. However, rcu_torture_cleanup() has not yet called kthread_stop() on those threads, and before it gets a chance to do so, multiple instances of torture_kthread_stopping() invoke schedule_timeout_interruptible(1) in a tight loop. Tracing confirms that TIMER_SOFTIRQ can then continuously execute timer callbacks. If that TIMER_SOFTIRQ preempts the task executing rcu_torture_cleanup(), that task might never invoke kthread_stop(). This commit improves this situation by increasing the timeout passed to schedule_timeout_interruptible() from one jiffy to 1/20th of a second. This change prevents TIMER_SOFTIRQ from monopolizing its CPU, thus allowing rcu_torture_cleanup() to carry out the needed kthread_stop() invocations. Testing has shown 100 runs of TREE07 passing reliably, as oppose to the tens-of-percent failure rates seen beforehand. Cc: Paul McKenney Cc: Frederic Weisbecker Cc: Zhouyi Zhou Cc: # 6.0.x Signed-off-by: Joel Fernandes (Google) Tested-by: Zhouyi Zhou Reviewed-by: Davidlohr Bueso Signed-off-by: Paul E. McKenney Signed-off-by: Greg Kroah-Hartman --- kernel/torture.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/kernel/torture.c +++ b/kernel/torture.c @@ -915,7 +915,7 @@ void torture_kthread_stopping(char *titl VERBOSE_TOROUT_STRING(buf); while (!kthread_should_stop()) { torture_shutdown_absorb(title); - schedule_timeout_uninterruptible(1); + schedule_timeout_uninterruptible(HZ / 20); } } EXPORT_SYMBOL_GPL(torture_kthread_stopping);