Messages in this thread | | | Date | Sat, 31 Jan 2009 20:49:10 +0300 | Subject | Re: [git pull] scheduler fixes | From | Alexey Zaytsev <> |
| |
On Sat, Jan 31, 2009 at 20:23, Peter Zijlstra <peterz@infradead.org> wrote: > On Sat, 2009-01-31 at 18:11 +0100, Peter Zijlstra wrote: >> > diff --git a/kernel/sched.c b/kernel/sched.c >> > index 52bbf1c..5686bb5 100644 >> > --- a/kernel/sched.c >> > +++ b/kernel/sched.c >> > @@ -4440,7 +4450,7 @@ void __kprobes sub_preempt_count(int val) >> > /* >> > * Underflow? >> > */ >> > - if (DEBUG_LOCKS_WARN_ON(val > preempt_count())) >> > + if (DEBUG_LOCKS_WARN_ON(val > preempt_count() - (!!kernel_locked()))) >> > return; >> > /* >> > * Is the spinlock portion underflowing? > > Since the commit msg of 01e3eb8 says: > > kernel_locked() is not a valid test in IRQ context (we update the > BKL's ->lock_depth and the preempt count separately and non-atomicalyy), > so we cannot put it into the generic preempt debugging checks which > can run in IRQ contexts too. >
Is the comment actually valid? From arch/x86/kernel/irq_32.c: do_softirq() actually does curctx = current_thread_info(); irqctx = softirq_ctx[smp_processor_id()]; irqctx->tinfo.task = curctx->task;
and so does execute_on_irq_stack(). So kernel_locked() should be valid. It corresponds to the thread that is being interrupted.
And answering an earlier question, this happens only on i386 and only with 4K stacks because x86_64 dosn't have a separate softirq stack, so the preempt count diring the soft irq is at least IRQ_EXIT_OFFSET.
(If I understood the things correctly)
> Another possibility would be writing it like: > > if (DEBUG_LOCKS_WARN_ON(val > preempt_count() - > (in_interrupt() ? 0 : !!kernel_locked()))) > > Which might just work because we're in sub_preempt_count, before we > actually do the subtraction, so in_interrupt() will still be true. > > > >
| |