Messages in this thread |  | | | Date | Sat, 31 Jan 2009 18:54:32 +0100 | | From | Ingo Molnar <> | | Subject | Re: [git pull] scheduler fixes |
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* Alexey Zaytsev <alexey.zaytsev@gmail.com> wrote:
> 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)
Correct, on 64-bit we use the hardirq stack for softirqs too:
ENTRY(call_softirq) CFI_STARTPROC push %rbp CFI_ADJUST_CFA_OFFSET 8 CFI_REL_OFFSET rbp,0 mov %rsp,%rbp CFI_DEF_CFA_REGISTER rbp incl PER_CPU_VAR(irq_count) cmove PER_CPU_VAR(irq_stack_ptr),%rsp push %rbp # backlink for old unwinder call __do_softirq
Ingo
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