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SubjectRe: sys_sched_yield keeps locked irq before call of schedule()

On Thu, 6 Nov 2008, Ingo Molnar wrote:
>
> * Zdenek Kabelac <zdenek.kabelac@gmail.com> wrote:
>
> > > is this some special warning you added? The stock kernel certainly
> > > does not emit this warning.
> >
> > Yes - it's my personal debug checker that tries to watch wether irq
> > & irqsafe are running in pair. So it shows a warning if there is a
> > call of spin_lock_irq and irq is already dissabled.
>
> btw., i have added lockdep instrumentation for this two years ago,
> it's in the upstream kernel:
>
> /proc/lockdep_stats: redundant hardirq ons: 7744
> /proc/lockdep_stats: redundant hardirq offs: 1873736
> /proc/lockdep_stats: redundant softirq ons: 0
> /proc/lockdep_stats: redundant softirq offs: 0
>
> you could extend the code to trace it. See
> kernel/lockdep.c:trace_hardirqs_on_caller(). This bit does it:
>
> if (unlikely(curr->hardirqs_enabled)) {
> debug_atomic_inc(&redundant_hardirqs_on);
> return;
> }
>
> you could add a ftrace_printk("redundant hardirq") call right there,
> enable ftrace, and enable stack tracing of each trace entry:

Quick note. Currently ftrace_printk only shows up if it is set in the
iter_ctrl.

echo trace_printk > /debug/tracing/iter_ctrl
I'll send out a patch to have it on by default.

-- Steve

>
> echo stacktrace > /debug/tracing/iter_ctrl
>
> then you should see all the call sites in /debug/tracing/trace.
>
> Ingo
>
>


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