diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2014-02-11 16:01:16 +0100 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2014-02-21 21:49:07 +0100 |
| commit | cd578abb24aa67ce468c427d3356c08ea32cf768 (patch) | |
| tree | 974a97cebfc368e8bee9c1beccbbd9bda00d89ef /kernel | |
| parent | 90ed5b0fa5eb96e1cbb34aebf6a9ed96ee1587ec (diff) | |
perf/x86: Warn to early_printk() in case irq_work is too slow
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: 6a02ad66b2c4 ("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>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/events/core.c | 9 | ||||
| -rw-r--r-- | kernel/irq_work.c | 6 |
2 files changed, 11 insertions, 4 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index 2067cbb378eb..45e5543e2a1e 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -243,7 +243,7 @@ static void perf_duration_warn(struct irq_work *w) printk_ratelimited(KERN_WARNING "perf interrupt took too long (%lld > %lld), lowering " "kernel.perf_event_max_sample_rate to %d\n", - avg_local_sample_len, allowed_ns, + avg_local_sample_len, allowed_ns >> 1, sysctl_perf_event_sample_rate); } @@ -283,7 +283,12 @@ void perf_sample_event_took(u64 sample_len_ns) update_perf_cpu_limits(); - irq_work_queue(&perf_duration_work); + if (!irq_work_queue(&perf_duration_work)) { + early_printk("perf interrupt took too long (%lld > %lld), lowering " + "kernel.perf_event_max_sample_rate to %d\n", + avg_local_sample_len, allowed_ns >> 1, + sysctl_perf_event_sample_rate); + } } static atomic64_t perf_event_id; diff --git a/kernel/irq_work.c b/kernel/irq_work.c index 55fcce6065cf..a82170e2fa78 100644 --- a/kernel/irq_work.c +++ b/kernel/irq_work.c @@ -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); |