linux-kernel - [PATCH] perf_event: Make software events work again

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Message-ID: <20100508105800.GB10650@brick.ozlabs.ibm.com>
Date:	Sat, 8 May 2010 20:58:00 +1000
From:	Paul Mackerras <paulus@...ba.org>
To:	Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>,
	Lin Ming <ming.m.lin@...el.com>,
	Frederic Weisbecker <fweisbec@...il.com>, eranian@...il.com
Cc:	linux-kernel@...r.kernel.org
Subject: [PATCH] perf_event: Make software events work again

Commit 6bde9b6ce0127e2a56228a2071536d422be31336 ("perf: Add group
scheduling transactional APIs") added code to allow a group to be
scheduled in a single transaction.  However, it introduced a bug in
handling events whose pmu does not implement transactions -- at the
end of scheduling in the events in the group, in the non-transactional
case the code now falls through to the group_error label, and proceeds
to unschedule all the events in the group and return failure.

This fixes it by returning 0 (success) in the non-transactional case.

Signed-off-by: Paul Mackerras <paulus@...ba.org>
---
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index bb06382..180151f 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -664,13 +664,13 @@ group_sched_in(struct perf_event *group_event,
 		}
 	}

-	if (txn) {
-		ret = pmu->commit_txn(pmu);
-		if (!ret) {
-			pmu->cancel_txn(pmu);
+	if (!txn)
+		return 0;

-			return 0;
-		}
+	ret = pmu->commit_txn(pmu);
+	if (!ret) {
+		pmu->cancel_txn(pmu);
+		return 0;
 	}

 group_error:
--
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