* [PATCH -rt] fix preempt count underflow in user_trace_stop
@ 2007-03-12 16:03 Michal Schmidt
2007-03-12 16:46 ` Ingo Molnar
0 siblings, 1 reply; 2+ messages in thread
From: Michal Schmidt @ 2007-03-12 16:03 UTC (permalink / raw)
To: Ingo Molnar; +Cc: Thomas Gleixner, linux-kernel
When playing with trace_user_trigger_irq in order to trace
IRQ->userspace latencies, I encountered a bug in the latency tracer. If
I have wakeup_timing enabled and attempt to stop the trace in my
userspace program, the system crashes. This is caused by an unbalanced
preempt_enable() which underflows the preempt count.
Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
diff --git a/kernel/latency_trace.c b/kernel/latency_trace.c
index e07bb95..29dfb79 100644
--- a/kernel/latency_trace.c
+++ b/kernel/latency_trace.c
@@ -2396,7 +2396,6 @@ long user_trace_stop(void)
if (current != sch.task) {
__raw_spin_unlock(&sch.trace_lock);
local_irq_restore(flags);
- preempt_enable();
return -EINVAL;
}
sch.task = NULL;
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH -rt] fix preempt count underflow in user_trace_stop
2007-03-12 16:03 [PATCH -rt] fix preempt count underflow in user_trace_stop Michal Schmidt
@ 2007-03-12 16:46 ` Ingo Molnar
0 siblings, 0 replies; 2+ messages in thread
From: Ingo Molnar @ 2007-03-12 16:46 UTC (permalink / raw)
To: Michal Schmidt; +Cc: Thomas Gleixner, linux-kernel
* Michal Schmidt <mschmidt@redhat.com> wrote:
> When playing with trace_user_trigger_irq in order to trace
> IRQ->userspace latencies, I encountered a bug in the latency tracer.
> If I have wakeup_timing enabled and attempt to stop the trace in my
> userspace program, the system crashes. This is caused by an unbalanced
> preempt_enable() which underflows the preempt count.
good catch! I've applied it,
Ingo
^ permalink raw reply [flat|nested] 2+ messages in thread
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2007-03-12 16:03 [PATCH -rt] fix preempt count underflow in user_trace_stop Michal Schmidt
2007-03-12 16:46 ` Ingo Molnar
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