From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f72.google.com (mail-pg0-f72.google.com [74.125.83.72]) by kanga.kvack.org (Postfix) with ESMTP id 20B4D6B0038 for ; Mon, 30 Oct 2017 11:10:24 -0400 (EDT) Received: by mail-pg0-f72.google.com with SMTP id y5so13776403pgq.15 for ; Mon, 30 Oct 2017 08:10:24 -0700 (PDT) Received: from bombadil.infradead.org (bombadil.infradead.org. [65.50.211.133]) by mx.google.com with ESMTPS id e22si9593897plj.603.2017.10.30.08.10.22 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 30 Oct 2017 08:10:22 -0700 (PDT) Date: Mon, 30 Oct 2017 16:10:09 +0100 From: Peter Zijlstra Subject: Re: possible deadlock in lru_add_drain_all Message-ID: <20171030151009.ip4k7nwan7muouca@hirez.programming.kicks-ass.net> References: <089e0825eec8955c1f055c83d476@google.com> <20171027093418.om5e566srz2ztsrk@dhcp22.suse.cz> <20171027134234.7dyx4oshjwd44vqx@dhcp22.suse.cz> <20171030082203.4xvq2af25shfci2z@dhcp22.suse.cz> <20171030100921.GA18085@X58A-UD3R> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171030100921.GA18085@X58A-UD3R> Sender: owner-linux-mm@kvack.org List-ID: To: Byungchul Park Cc: Michal Hocko , Dmitry Vyukov , syzbot , Andrew Morton , Dan Williams , Johannes Weiner , Jan Kara , jglisse@redhat.com, LKML , linux-mm@kvack.org, shli@fb.com, syzkaller-bugs@googlegroups.com, Thomas Gleixner , Vlastimil Babka , ying.huang@intel.com, kernel-team@lge.com On Mon, Oct 30, 2017 at 07:09:21PM +0900, Byungchul Park wrote: > On Mon, Oct 30, 2017 at 09:22:03AM +0100, Michal Hocko wrote: > > [Cc Byungchul. The original full report is > > http://lkml.kernel.org/r/089e0825eec8955c1f055c83d476@google.com] > > > > Could you have a look please? This smells like a false positive to me. > > +cc peterz@infradead.org > > Hello, > > IMHO, the false positive was caused by the lockdep_map of 'cpuhp_state' > which couldn't distinguish between cpu-up and cpu-down. > > And it was solved with the following commit by Peter and Thomas: > > 5f4b55e10645b7371322c800a5ec745cab487a6c > smp/hotplug: Differentiate the AP-work lockdep class between up and down > > Therefore, we can avoid the false positive on later than the commit. > > Peter and Thomas, could you confirm it? I can indeed confirm it's running old code; cpuhp_state is no more. However, that splat translates like: __cpuhp_setup_state() #0 cpus_read_lock() __cpuhp_setup_state_cpuslocked() #1 mutex_lock(&cpuhp_state_mutex) __cpuhp_state_add_instance() #2 mutex_lock(&cpuhp_state_mutex) cpuhp_issue_call() cpuhp_invoke_ap_callback() #3 wait_for_completion() msr_device_create() ... #4 filename_create() #3 complete() do_splice() #4 file_start_write() do_splice_from() iter_file_splice_write() #5 pipe_lock() vfs_iter_write() ... #6 inode_lock() sys_fcntl() do_fcntl() shmem_fcntl() #5 inode_lock() shmem_wait_for_pins() if (!scan) lru_add_drain_all() #0 cpus_read_lock() Which is an actual real deadlock, there is no mixing of up and down. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org