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perf/x86: Warn to early_printk() in case irq_work is too slow

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On Mon, Feb 10, 2014 at 08:45:16AM -0800, Dave Hansen wrote:
> The reason I coded this up was that NMIs were firing off so fast that
> nothing else was getting a chance to run.  With this patch, at least the
> printk() would come out and I'd have some idea what was going on.

It will start spewing to early_printk() (which is a lot nicer to use
from NMI context too) when it fails to queue the IRQ-work because its
already enqueued.

It does have the false-positive for when two CPUs trigger the warn
concurrently, but that should be rare and some extra clutter on the
early printk shouldn't be a problem.

Cc: hpa@zytor.com
Cc: tglx@linutronix.de
Cc: dzickus@redhat.com
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: mingo@kernel.org
Fixes: 6a02ad66b2 ("perf/x86: Push the duration-logging printk() to IRQ context")
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20140211150116.GO27965@twins.programming.kicks-ass.net
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Peter Zijlstra 2014-02-11 16:01:16 +01:00 • committed by Thomas Gleixner
parent 90ed5b0fa5
commit cd578abb24
3 changed files with 12 additions and 5 deletions
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6
kernel/irq_work.c
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@ -61,11 +61,11 @@ void __weak arch_irq_work_raise(void)
*
* Can be re-enqueued while the callback is still in progress.
*/
void irq_work_queue(struct irq_work *work)
bool irq_work_queue(struct irq_work *work)
{
/* Only queue if not already pending */
if (!irq_work_claim(work))
return;
return false;
/* Queue the entry and raise the IPI if needed. */
preempt_disable();
@ -83,6 +83,8 @@ void irq_work_queue(struct irq_work *work)
}
preempt_enable();
return true;
}
EXPORT_SYMBOL_GPL(irq_work_queue);