On 4/22/19 10:48 AM, Linus Torvalds wrote: > On Mon, Apr 22, 2019 at 9:38 AM Jens Axboe <axboe@xxxxxxxxx> wrote: >> >> With the mutex change in, I can trigger it in a second or so. Just ran >> the reproducer with that change reverted, and I'm not seeing any badness. >> So I do wonder if the bisect results are accurate? > > Looking at the syzbot report, it's syzbot being confused. > > The actual WARNING in percpu_ref_kill_and_confirm() only happens with > recent kernels. > > But then syzbot mixes it up with a completely different bug: > > crash: BUG: MAX_STACK_TRACE_ENTRIES too low! > BUG: MAX_STACK_TRACE_ENTRIES too low! > > and for some reason decides that *that* bug is the same thing entirely. > > So yeah, I think the simple percpu_ref_is_dying() check is sufficient, > and that the syzbot bisection is completely bogus. Ah good, that makes me feel better. I'll queue the fix up, thanks. -- Jens Axboe
