Messages in this thread | | | Date | Tue, 6 Jan 2015 03:07:30 -0800 | From | Kent Overstreet <> | Subject | Re: Linux 3.19-rc3 |
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On Tue, Jan 06, 2015 at 12:01:12PM +0100, Peter Zijlstra wrote: > On Tue, Jan 06, 2015 at 11:18:04AM +0100, Sedat Dilek wrote: > > On Tue, Jan 6, 2015 at 11:06 AM, Peter Zijlstra <peterz@infradead.org> wrote: > > > On Tue, Jan 06, 2015 at 10:57:19AM +0100, Sedat Dilek wrote: > > >> [ 88.028739] [<ffffffff8124433f>] aio_read_events+0x4f/0x2d0 > > >> > > > > > > Ah, that one. Chris Mason and Kent Overstreet were looking at that one. > > > I'm not touching the AIO code either ;-) > > > > I know, I was so excited when I see nearly the same output. > > > > Can you tell me why people see "similiar" problems in different areas? > > Because the debug check is new :-) It's a pattern that should not be > used but mostly works most of the times. > > > [ 181.397024] WARNING: CPU: 0 PID: 2872 at kernel/sched/core.c:7303 > > __might_sleep+0xbd/0xd0() > > [ 181.397028] do not call blocking ops when !TASK_RUNNING; state=1 > > set at [<ffffffff810b83bd>] prepare_to_wait_event+0x5d/0x110 > > > > With similiar buzzwords... namely... > > > > mutex_lock_nested > > prepare_to_wait(_event) > > __might_sleep > > > > I am asking myself... Where is the real root cause - in sched/core? > > Fix one single place VS. fix the impact at several other places? > > No, the root cause is nesting sleep primitives, this is not fixable in > the one place, both prepare_to_wait and mutex_lock are using > task_struct::state, they have to, no way around it.
No, it's completely possible to construct a prepare_to_wait() that doesn't require messing with the task state. Had it for years.
http://evilpiepirate.org/git/linux-bcache.git/log/?h=aio_ring_fix
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