Peter Zijlstra wrote:
According to Steve, we are already in an interrupt-disabled section here, but I will defer to him. He suggested I try this over an IRC conversation when I noticed a strange wakeup trace, and it seems to have solved the problem.On Tue, 2008-08-19 at 05:19 -0400, Gregory Haskins wrote:Suggested by Steve Rostedt to fix an observed "+1" in the preempt-count Signed-off-by: Gregory Haskins <ghaskins@xxxxxxxxxx> --- kernel/trace/trace_sched_wakeup.c | 2 ++ 1 files changed, 2 insertions(+), 0 deletions(-) diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c index c3a15bd..ae523fd 100644 --- a/kernel/trace/trace_sched_wakeup.c +++ b/kernel/trace/trace_sched_wakeup.c @@ -70,7 +70,9 @@ wakeup_tracer_call(unsigned long ip, unsigned long parent_ip) if (task_cpu(wakeup_task) != cpu) goto unlock;+ preempt_enable_no_resched_notrace();trace_function(tr, data, ip, parent_ip, flags); + preempt_disable_notrace();Is preempt_count > 1 at all times here? If not, it might drop to 0 and any interrupt might cause preemption - and its not obvious to me that that is actually correct.
Im really sending this patch more of a reminder to Steve that he was going to fix this, rather than to accept my patch as is. Of course I don't mind if it is accepted as is, and I can make the prologue/comments more descriptive if necessary. But if Steve wants to do something like fold this into his ftrace series, that is fine too. I just didn't want it to be forgotten ;)
-Greg
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