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

* 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:

echo stacktrace > /debug/tracing/iter_ctrl

then you should see all the call sites in /debug/tracing/trace.

Ingo


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