Messages in this thread | | | From | Divyesh Shah <> | Date | Fri, 11 Jun 2010 18:54:48 -0700 | Subject | Re: BUG: using smp_processor_id() in preemptible [00000000] code: icedove-bin/5449 |
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On Tue, Jun 1, 2010 at 12:53 AM, Jens Axboe <axboe@kernel.dk> wrote: > 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, Thanks for the temporary fix (adding preempt_enable/disable() calls). I was able to repro the issue and and have a patch that replaces use of sched_clock() in block layer w/ ktime_to_ns(ktime_get()). We will lose resolution when running w/o highres timers but should be better than unbounded drift between cpus. I'll send the patch next.
-Divyesh
> > -- > Jens Axboe > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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