linux-kernel - [tip: perf/urgent] perf: Fix event multiplexing for exclusive groups

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Message-ID: <160501231817.11244.16475577084391904219.tip-bot2@tip-bot2>
Date:   Tue, 10 Nov 2020 12:45:18 -0000
From:   "tip-bot2 for Peter Zijlstra" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     Andi Kleen <ak@...ux.intel.com>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: perf/urgent] perf: Fix event multiplexing for exclusive groups

The following commit has been merged into the perf/urgent branch of tip:

Commit-ID:     2714c3962f304d031d5016c963c4b459337b0749
Gitweb:        https://git.kernel.org/tip/2714c3962f304d031d5016c963c4b459337b0749
Author:        Peter Zijlstra <peterz@...radead.org>
AuthorDate:    Thu, 29 Oct 2020 16:29:53 +01:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 09 Nov 2020 18:12:36 +01:00

perf: Fix event multiplexing for exclusive groups

Commit 9e6302056f80 ("perf: Use hrtimers for event multiplexing")
placed the hrtimer (re)start call in the wrong place.  Instead of
capturing all scheduling failures, it only considered the PMU failure.

The result is that groups using perf_event_attr::exclusive are no
longer rotated.

Fixes: 9e6302056f80 ("perf: Use hrtimers for event multiplexing")
Reported-by: Andi Kleen <ak@...ux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Link: https://lkml.kernel.org/r/20201029162902.038667689@infradead.org
---
 kernel/events/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index f0e5268..00be48a 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2612,7 +2612,6 @@ group_error:
 
 error:
 	pmu->cancel_txn(pmu);
-	perf_mux_hrtimer_restart(cpuctx);
 	return -EAGAIN;
 }
 
@@ -3672,6 +3671,7 @@ static int merge_sched_in(struct perf_event *event, void *data)
 
 		*can_add_hw = 0;
 		ctx->rotate_necessary = 1;
+		perf_mux_hrtimer_restart(cpuctx);
 	}
 
 	return 0;