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    SubjectRe: 2.5 Problem Status Report

    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:

    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:


    #define dec_preempt_count() \
    do { \
    if (!--preempt_count()) \
    BUG(); \
    } while (0)


    #define dec_preempt_count() \
    do { \
    preempt_count()--; \
    } while (0)


    or introduce a separate debug config option, CONFIG_DEBUG_PREEMPT - until
    all code is converted. This should catch a bad preempt_enable where it


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