Re: [patch] voluntary-preempt-2.6.9-rc1-bk4-R3

From: K.R. Foley
Date: Fri Sep 03 2004 - 14:59:11 EST


Ingo Molnar wrote:
* Ingo Molnar <mingo@xxxxxxx> wrote:


i'll add a new feature to debug this: when crashing on an assert and
tracing is enabled the trace leading up to the crash will be printed
to the console. [...]


the -R3 patch has this feature:

http://redhat.com/~mingo/voluntary-preempt/voluntary-preempt-2.6.9-rc1-bk4-R3

you can enable it via enabling CONFIG_LATENCY_TRACE and doing:

echo 3 > /proc/sys/kernel/trace_enabled

it's all automatic from this point on: tracing will happen nonstop and
any assert or crash that prints the process stack will also print the
last 100 trace entries. Sample output:

Call Trace:
[<c0160401>] sys_munmap+0x61/0x80
[<c010520d>] sysenter_past_esp+0x52/0x71
Last 100 trace entries:
00000001: zap_pmd_range+0xe/0x90 <= (unmap_page_range+0x55/0x80)
00000001: stop_trace+0x8/0x20 <= (bust_spinlocks+0x20/0x60)
00000001: bust_spinlocks+0xe/0x60 <= (die+0xbc/0x2a0)
[... 97 more trace entries ...]

Please capture and mail the first 'extended' oops that triggers
(secondary followup traces are probably just side-effects of the crash),
it could give us clues about where the bug is.

Ingo


Building now.

kr
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