Commit-ID: cd578abb24aa67ce468c427d3356c08ea32cf768
Gitweb: http://git.kernel.org/tip/cd578abb24aa67ce468c427d3356c08ea32cf768
Author: Peter Zijlstra <pet...@infradead.org>
AuthorDate: Tue, 11 Feb 2014 16:01:16 +0100
Committer: Thomas Gleixner <t...@linutronix.de>
CommitDate: Fri, 21 Feb 2014 21:49:07 +0100
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: h...@zytor.com
Cc: t...@linutronix.de
Cc: dzic...@redhat.com
Cc: Dave Hansen <dave.han...@linux.intel.com>
Cc: mi...@kernel.org
Fixes: 6a02ad66b2c4 ("perf/x86: Push the duration-logging printk() to IRQ
context")
Signed-off-by: Peter Zijlstra <pet...@infradead.org>
Link:
http://lkml.kernel.org/r/20140211150116.go27...@twins.programming.kicks-ass.net
Signed-off-by: Thomas Gleixner <t...@linutronix.de>
---
include/linux/irq_work.h | 2 +-
kernel/events/core.c | 9 +++++++--
kernel/irq_work.c | 6 ++++--
3 files changed, 12 insertions(+), 5 deletions(-)
diff --git a/include/linux/irq_work.h b/include/linux/irq_work.h
index add13c8..19ae05d 100644
--- a/include/linux/irq_work.h
+++ b/include/linux/irq_work.h
@@ -32,7 +32,7 @@ void init_irq_work(struct irq_work *work, void (*func)(struct
irq_work *))
#define DEFINE_IRQ_WORK(name, _f) struct irq_work name = { .func = (_f), }
-void irq_work_queue(struct irq_work *work);
+bool irq_work_queue(struct irq_work *work);
void irq_work_run(void);
void irq_work_sync(struct irq_work *work);
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 2067cbb..45e5543 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 55fcce6..a82170e 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);
--
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