On Wed, Aug 23, 2017 at 11:36:49AM +0900, Sergey Senozhatsky wrote: > On (08/23/17 09:03), Byungchul Park wrote: > [..] > > aha, ok > > > The report is talking about the following lockup: > > > > A work in a worker A task work on exit to user > > ------------------ --------------------------- > > mutex_lock(&bdev->bd_mutex) > > mutext_lock(&bdev->bd_mutex) > > blk_execute_rq() > > wait_for_completion_io_timeout(&A) > > complete(&A) > > > > Is this impossible? > > I was really confused how this "unlock" may lead to a deadlock Hi Sergey, Right. It should be enhanced. > > > > > other info that might help us debug this: > > > > Possible unsafe locking scenario by crosslock: > > > > CPU0 CPU1 > > > > ---- ---- > > > > lock(&bdev->bd_mutex); > > > > lock((complete)&wait#2); > > > > lock(&bdev->bd_mutex); > > > > unlock((complete)&wait#2); > > > any chance the report can be improved? mention timeout, etc? > // well, if this functionality will stay. > > > p.s. > Bart Van Assche, thanks for Cc-ing Park Byungchul, I was really > sure I didn't enabled the cross-release, but apparently I was wrong: > CONFIG_LOCKDEP_CROSSRELEASE=y > CONFIG_LOCKDEP_COMPLETIONS=y > > -ss
