On Fri, Oct 27, 2017 at 11:44 AM, Dmitry Vyukov <dvyukov@xxxxxxxxxx> wrote: > On Fri, Oct 27, 2017 at 11:34 AM, Michal Hocko <mhocko@xxxxxxxxxx> wrote: >> On Fri 27-10-17 02:22:40, syzbot wrote: >>> Hello, >>> >>> syzkaller hit the following crash on >>> a31cc455c512f3f1dd5f79cac8e29a7c8a617af8 >>> git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/master >>> compiler: gcc (GCC) 7.1.1 20170620 >>> .config is attached >>> Raw console output is attached. >> >> I do not see such a commit. My linux-next top is next-20171018 As far as I understand linux-next constantly recreates tree, so that all commits hashes are destroyed. Somebody mentioned some time ago about linux-next-something tree which keeps all of the history (but I don't remember it off the top of my head). >> [...] >>> Chain exists of: >>> cpu_hotplug_lock.rw_sem --> &pipe->mutex/1 --> &sb->s_type->i_mutex_key#9 >>> >>> Possible unsafe locking scenario: >>> >>> CPU0 CPU1 >>> ---- ---- >>> lock(&sb->s_type->i_mutex_key#9); >>> lock(&pipe->mutex/1); >>> lock(&sb->s_type->i_mutex_key#9); >>> lock(cpu_hotplug_lock.rw_sem); >> >> I am quite confused about this report. Where exactly is the deadlock? >> I do not see where we would get pipe mutex from inside of the hotplug >> lock. Is it possible this is just a false possitive due to cross release >> feature? > > > As far as I understand this CPU0/CPU1 scheme works only for simple > cases with 2 mutexes. This seem to have larger cycle as denoted by > "the existing dependency chain (in reverse order) is:" section. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
