From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-170.mta0.migadu.com (out-170.mta0.migadu.com [91.218.175.170]) (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 63D8319049C for ; Thu, 8 Aug 2024 17:03:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.170 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723136603; cv=none; b=l6Nx6p596/aAA0ef8SMyKtLxXs+aqcfeOJFF+NOvSYTNNJDAm0AGDPUiVKHVP9qj7xqKUxTvC2zdYCxNj/3AuhAXxFCZ5ZsD+VpskBI0jmJMHSLuct2Efz8K/f/SWYCvml3c8vIGDLB/vN9BRw32LtqufsCLmDfBwQ4oUUWYFCs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1723136603; c=relaxed/simple; bh=ihQb0I3WgYoE2XrU+Z6LvbSlpPClAqC+qpIj0bqqqW4=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=qUbs2cMkvYb6uh+a7hBE6etUCt9iGq65l7jLJY2uTT6azHaPe1rUVdy4UtBthv1o1BGTBflVn2svdqHEOh7WhikNbdknN+0LfR4WeExvqn5wTy7p28LK2ofbtCPpq4G+OWVhHVl7SHcH7nLSRlJrr7HVR0oMi9Uzh7gxV41tio0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=wRUIUBQj; arc=none smtp.client-ip=91.218.175.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="wRUIUBQj" Date: Thu, 8 Aug 2024 17:03:14 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1723136599; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=PDecU1wXSp3ftwbMT3/0o0Lz4Kzs8iM6+w9Zo7Y8cYY=; b=wRUIUBQj28SOBua7hLGw5nG7c8/9hIuLN+e/6Q810vGKDzcBHIl2Cnhu/CC6zdvf269WoA nmuy1s35EYHqWRrjPj1S6qhEVW8CVMFaQlR8TvVwzx7FbQSUd9dmugCvDD7XPHRXcUp/97 Q5XpvEkZGpTjtSKI85ZgkdHYJzuNVYo= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Roman Gushchin To: Michal =?iso-8859-1?Q?Koutn=FD?= Cc: chenridong , Hillf Danton , tj@kernel.org, bpf@vger.kernel.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH -v2] cgroup: fix deadlock caused by cgroup_mutex and cpu_hotplug_lock Message-ID: References: <20240724110834.2010-1-hdanton@sina.com> <53ed023b-c86c-498a-b1fc-2b442059f6af@huawei.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=us-ascii Content-Disposition: inline In-Reply-To: X-Migadu-Flow: FLOW_OUT On Wed, Aug 07, 2024 at 03:32:59PM +0200, Michal Koutny wrote: > Hello. > > On Sat, Jul 27, 2024 at 06:21:55PM GMT, chenridong wrote: > > Yes, I have offered the scripts in Link(V1). > > Thanks (and thanks for patience). > There is no lockdep complain about a deadlock (i.e. some circular > locking dependencies). (I admit the multiple holders of cgroup_mutex > reported there confuse me, I guess that's an artifact of this lockdep > report and they could be also waiters.) > > ... > > The change on its own (deferred cgroup bpf progs removal via > cgroup_destroy_wq instead of system_wq) is sensible by collecting > related objects removal together (at the same time it shouldn't cause > problems by sharing one cgroup_destroy_wq). > > But the reasoning in the commit message doesn't add up to me. There > isn't obvious deadlock, I'd say that system is overloaded with repeated > calls of __lockup_detector_reconfigure() and it is not in deadlock > state -- i.e. when you stop the test, it should eventually recover. Thanks, Michal! I've exactly same feelings about this change.