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SubjectRe: BUG: using smp_processor_id() in preemptible [00000000] code: icedove-bin/5449
On Tue, Jun 01 2010, Ingo Molnar wrote:
>
> * Jens Axboe <axboe@kernel.dk> wrote:
>
> > On Tue, Jun 01 2010, Ingo Molnar wrote:
> > >
> > > * Peter Zijlstra <peterz@infradead.org> wrote:
> > >
> > > > On Mon, 2010-05-24 at 05:03 +0200, Piotr Hosowicz wrote:
> > > > > [ 720.313607] BUG: using smp_processor_id() in preemptible [00000000] code: icedove-bin/5449
> > > > > [ 720.313612] caller is native_sched_clock+0x3c/0x68
> > > > > [ 720.313616] Pid: 5449, comm: icedove-bin Tainted: P 2.6.34-20100524-0407 #1
> > > > > [ 720.313618] Call Trace:
> > > > > [ 720.313624] [<ffffffff811a533b>] debug_smp_processor_id+0xc7/0xe0
> > > > > [ 720.313629] [<ffffffff81009b87>] native_sched_clock+0x3c/0x68
> > > > > [ 720.313634] [<ffffffff81009a4d>] sched_clock+0x9/0xd
> > > > > [ 720.313637] [<ffffffff811823ec>] blk_rq_init+0x92/0x9d
> > > > > [ 720.313641] [<ffffffff81184227>] get_request+0x1bf/0x2c7
> > > > > [ 720.313646] [<ffffffff8118435c>] get_request_wait+0x2d/0x19d
> > > >
> > > > This comes from wreckage in the blk tree..
> > > >
> > > > ---
> > > > commit 9195291e5f05e01d67f9a09c756b8aca8f009089
> > > > Author: Divyesh Shah <dpshah@google.com>
> > > > Date: Thu Apr 1 15:01:41 2010 -0700
> > > >
> > > > blkio: Increment the blkio cgroup stats for real now
> > >
> > > Jens, this regression is still in .35-rc1 and triggers in about 25% of all
> > > -tip boot tests.
> > >
> > > The above commit is using sched_clock() in an unsafe way - please fix it or
> > > revert it.
> > >
> > > The local_clock() changes PeterZ is working on are still WIP, it's not sure
> > > we'll have it before .36.
> >
> > OK, I guess we'll have to solve this differently for .35 - I'll cook up
> > something simple, if need be revert the change.
>
> I suspect you can put get_cpu/put_cpu around it and use cpu_clock(). The
> cross-CPU effects will still be there and there might be weird stats.

It'll shut it up at least, which is the primary concern at this point.

--
Jens Axboe



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