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 DCE831C4612 for ; Wed, 30 Oct 2024 23:42:25 +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=1730331748; cv=none; b=GDAjdkePCCLC+QgWrCjcZubPz8iRna3M1qWN4xiNv6SXjzAthQnNtFuLdRcW/HwrQ5Un8HoUbgeQHy3IjvbR3dLG5XKmtqKFFyrxN1l+K9n1wrBPRcOF72klQR/YPBB6Thfy8FyAu1sIUcI/EUmCDJsELXB9GdbN3n3LXZswzsc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1730331748; c=relaxed/simple; bh=k9bOMp2HT61Oej6gu2Ql5vK88fG8w93+kfnnHQ5wPv8=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=GEJT5ew+ik3bPgy5hX4y8haxWbhsCOjypyqpDc0Fq1w0TpWB9ZKBB8O4KH+6KlmY03DDLoz5ST+SZrEC1xZmWisChkK/9a3ZV4FQaCVG92HdSPe94JoKIWf6jRzUcfbpzt5YYVwe+Qkcg2JKWgDnEIqgjC1pnGxAgDRS2HKVXQ8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=oVbQ6/y7; 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="oVbQ6/y7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 44405C4FE92; Wed, 30 Oct 2024 23:42:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1730331745; bh=k9bOMp2HT61Oej6gu2Ql5vK88fG8w93+kfnnHQ5wPv8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=oVbQ6/y7DHsQGEQ1iugbnsUsqvrip1Ym/Ud33S9lTm+jCt+52prExPSE/FexK1l7i 4oA0FGBZ3lJOYYWV0BL0jOaOyCw79lhCqq/ETR2PvqSJiLW2jxUDLwtBSvMTtHekOF 9BKPM1dsePGU1VIvpfNepE0YmkHBko6nBrvc5Js27THk+dPcV+lwYd2aLjr+WQbQoT UqQi8M6GcaDxyAXF/Ut6SEUmTkacSfsfg+w6/RV7AwTs9dvX8BvpLLn5dldt907rY3 mwAMrMycAaJYxct0+Z4WhaRG1kkeRxr2s/B3bbst6KmJTmGJN1xf12fBIswj90sdkN gz8xxeGc3q2Bw== Date: Wed, 30 Oct 2024 13:42:24 -1000 From: Tejun Heo To: Tim Chen Cc: Lai Jiangshan , linux-kernel@vger.kernel.org, Thomas Gleixner , Doug Nelson , bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, mingo@redhat.com, syzkaller-bugs@googlegroups.com, x86@kernel.org Subject: Re: BUG: Stall on adding/removing wokers into workqueue pool Message-ID: References: <1cf7b0dbfa4190eeaf0b3401bf7a991b8db59a59.camel@linux.intel.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1cf7b0dbfa4190eeaf0b3401bf7a991b8db59a59.camel@linux.intel.com> Hello, Tim. On Tue, Oct 29, 2024 at 03:03:33PM -0700, Tim Chen wrote: > Hi Tejun, > > Forwarding this task hung seen by my colleague Doug Nelson. He tested > the 6.12-rc4 kernel with an OLTP workload running on a 2 socket with > Granite Rapids CPU that has 86 cores per socket. The traces  > seem to indicate that the acquisition  > of wq_pool_attach_mutex stalled in idle_cull_fn() when removing worker from > the pool. Doug hit this problem occasionally in his tests. > > Searching through the bug reports, there's a similar report by szybot on the > 6.12-rc2 kernel. Szybot reported similar task hung when attaching workers to > the pool: https://lore.kernel.org/all/6706c4ba.050a0220.1139e6.0008.GAE@google.com/T/ > So we suspect that the problem is not GNR CPU specific. > > Wonder if this problem is a known one? First time I see it. The trace doesn't show who's holding the mutex. There doesn't seem to be any place where that mutex should leak at least on a glance, so hopefully it shouldn't be too difficult to find who's holding it. Can you trigger sysrq-d and sysrq-t and post the output? Thanks. -- tejun