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 D8B301094C for ; Mon, 8 May 2023 11:24:33 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 56573C433D2; Mon, 8 May 2023 11:24:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1683545073; bh=qsGsqDNzEEAAuLw5D7pi2FKVSXaQPg5MW2RmfWFuMPU=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=BTMjAhQQLHeL9IEugJU3HqcCvE3iuiF8/6reJrSYS2cKEsPO1nXHl79mfna3EASrQ UWG43gHUt8Z0o9HCV2U+uo75ZhOqz74184zx6hwI1oslREk4Obk7ShZeaDeC1PybxQ 3fSTdZJM2Dn3ZBTMFv5fEXsJDFo66UR90ER5J86o= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Petr Mladek , Tejun Heo , Sasha Levin Subject: [PATCH 6.3 584/694] workqueue: Fix hung time report of worker pools Date: Mon, 8 May 2023 11:46:59 +0200 Message-Id: <20230508094453.963193325@linuxfoundation.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230508094432.603705160@linuxfoundation.org> References: <20230508094432.603705160@linuxfoundation.org> User-Agent: quilt/0.67 Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Petr Mladek [ Upstream commit 335a42ebb0ca8ee9997a1731aaaae6dcd704c113 ] The workqueue watchdog prints a warning when there is no progress in a worker pool. Where the progress means that the pool started processing a pending work item. Note that it is perfectly fine to process work items much longer. The progress should be guaranteed by waking up or creating idle workers. show_one_worker_pool() prints state of non-idle worker pool. It shows a delay since the last pool->watchdog_ts. The timestamp is updated when a first pending work is queued in __queue_work(). Also it is updated when a work is dequeued for processing in worker_thread() and rescuer_thread(). The delay is misleading when there is no pending work item. In this case it shows how long the last work item is being proceed. Show zero instead. There is no stall if there is no pending work. Fixes: 82607adcf9cdf40fb7b ("workqueue: implement lockup detector") Signed-off-by: Petr Mladek Signed-off-by: Tejun Heo Signed-off-by: Sasha Levin --- kernel/workqueue.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/kernel/workqueue.c b/kernel/workqueue.c index b8b541caed485..2be9b0ecf22ce 100644 --- a/kernel/workqueue.c +++ b/kernel/workqueue.c @@ -5002,10 +5002,16 @@ static void show_one_worker_pool(struct worker_pool *pool) struct worker *worker; bool first = true; unsigned long flags; + unsigned long hung = 0; raw_spin_lock_irqsave(&pool->lock, flags); if (pool->nr_workers == pool->nr_idle) goto next_pool; + + /* How long the first pending work is waiting for a worker. */ + if (!list_empty(&pool->worklist)) + hung = jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000; + /* * Defer printing to avoid deadlocks in console drivers that * queue work while holding locks also taken in their write @@ -5014,9 +5020,7 @@ static void show_one_worker_pool(struct worker_pool *pool) printk_deferred_enter(); pr_info("pool %d:", pool->id); pr_cont_pool_info(pool); - pr_cont(" hung=%us workers=%d", - jiffies_to_msecs(jiffies - pool->watchdog_ts) / 1000, - pool->nr_workers); + pr_cont(" hung=%lus workers=%d", hung, pool->nr_workers); if (pool->manager) pr_cont(" manager: %d", task_pid_nr(pool->manager->task)); -- 2.39.2