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

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Message-ID: <AANLkTilwlZKx0k-Z_6LHVXIM561JLcWV4mX4Wcwgb7r0@mail.gmail.com>
Date:	Tue, 25 May 2010 18:10:06 +0200
From:	Stephane Eranian <eranian@...gle.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	eranian@...il.com, linux-kernel@...r.kernel.org, mingo@...e.hu,
	paulus@...ba.org, davem@...emloft.net, fweisbec@...il.com,
	acme@...radead.org, ming.m.lin@...el.com,
	perfmon2-devel@...ts.sf.net
Subject: Re: [PATCH] perf_events: fix event scheduling issues introduced by 
	transactional API (take 2)

> 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_
>                }
>        }
>
> -       if (!txn)
> +       if (!txn || !pmu->commit_txn(pmu))
>                return 0;
>
> -       ret = pmu->commit_txn(pmu);
> -       if (!ret) {
> -               pmu->cancel_txn(pmu);
> -               return 0;
> -       }
> -
>  group_error:
>        /*
>         * 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.