Messages in this thread |  | | Date | Wed, 11 Sep 2002 09:26:40 +0200 (CEST) | From | Ingo Molnar <> | Subject | Re: 2.5 Problem Status Report |
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On Wed, 11 Sep 2002, Oleg Drokin wrote:
> > > BUG at kernel/sched.c open 10 Sep 2002 > > What exactly is this? > > Looks like this is my bugreport for BUG in kernel/sched.c:944 in the middle > of partition parsing output on boot. > > Subject of email was > '2.5.34 BUG at kernel/sched.c:944 (partitions code related?)' > msgid: 20020910175639.A830@namesys.com
very strange backtrace:
>>EIP; c0115818 <schedule+18/4a0> <===== Trace; c01053a0 <default_idle+0/40> Trace; c0105000 <_stext+0/0> Trace; c01053c8 <default_idle+28/40> Trace; c010547e <cpu_idle+4e/50> Trace; c010506c <rest_init+6c/70>
i've once seen the 2.5 IDE code doing a schedule_timeout() from an IRQ handler, but the above has to be something else. Could you hack sched.c to print out the exact preemption count? It could be a preempt-count underflow due to an unbalanced spin_unlock, or an inbalanced preempt_enable. [or the IRQ code - but i doubt that, we'd have seen problems much earlier if this was the case.]
Oleg, do you have CONFIG_DEBUG_SPINLOCK enabled? That should catch an unbalanced spin_unlock().
Robert, i'd suggest to add some sort of debugging code for this anyway, if preempt_count goes below 0, right now we do this:
#define dec_preempt_count() \ do { \ preempt_count()--; \ } while (0)
this should be something like:
#if CONFIG_DEBUG_SPINLOCK
#define dec_preempt_count() \ do { \ if (!--preempt_count()) \ BUG(); \ } while (0)
#else
#define dec_preempt_count() \ do { \ preempt_count()--; \ } while (0)
#endif
or introduce a separate debug config option, CONFIG_DEBUG_PREEMPT - until all code is converted. This should catch a bad preempt_enable where it happens.
Ingo
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