Re: [PATCH] perf_events: fix event scheduling issues introduced by transactional API (take 2)

[Stephane Eranian]

On Tue, May 25, 2010 at 6:18 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> On Tue, 2010-05-25 at 18:10 +0200, Stephane Eranian wrote:
>> > Index: linux-2.6/kernel/perf_event.c
>> > ===================================================================
>> > --- linux-2.6.orig/kernel/perf_event.c
>> > +++ linux-2.6/kernel/perf_event.c
>> > @@ -668,15 +668,9 @@ group_sched_in(struct perf_event *group_
>> > Â Â Â Â Â Â Â Â}
>> > Â Â Â Â}
>> >
>> > - Â Â Â if (!txn)
>> > + Â Â Â if (!txn || !pmu->commit_txn(pmu))
>> > Â Â Â Â Â Â Â Âreturn 0;
>> >
>> > - Â Â Â ret = pmu->commit_txn(pmu);
>> > - Â Â Â if (!ret) {
>> > - Â Â Â Â Â Â Â pmu->cancel_txn(pmu);
>> > - Â Â Â Â Â Â Â return 0;
>> > - Â Â Â }
>> > -
>> > Âgroup_error:
>> > Â Â Â Â/*
>> > Â Â Â Â * Groups can be scheduled in as one unit only, so undo any
>> >
>> Looks okay.
>>
>> I believe you can also drop the txn test in group_sched_in() after group_error:,
>> given you have the if !(txn) return 0.
>
> Can't we still get in the group_error: branch with either scenario?
>
You're right. We must keep it because of failure in the siblings' loop.
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