[tip:perf/core] perf: Always switch pmu specific data during context switch

From: tip-bot for Yan, Zheng
Date: Wed Feb 18 2015 - 12:16:24 EST

Commit-ID: 5a158c3ccd2183a7b0866be6685d001fe653430f
Gitweb: http://git.kernel.org/tip/5a158c3ccd2183a7b0866be6685d001fe653430f
Author: Yan, Zheng <zheng.z.yan@xxxxxxxxx>
AuthorDate: Tue, 4 Nov 2014 21:56:02 -0500
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Wed, 18 Feb 2015 17:16:07 +0100

perf: Always switch pmu specific data during context switch

If two tasks were both forked from the same parent task, Events in
their perf task contexts can be the same. Perf core may leave out
switching the perf event contexts.

Previous patch inroduces pmu specific data. The data is for saving
the LBR stack, it is task specific. So we need to switch the data
even when context switch is optimized out.

Signed-off-by: Yan, Zheng <zheng.z.yan@xxxxxxxxx>
Signed-off-by: Kan Liang <kan.liang@xxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: eranian@xxxxxxxxxx
Cc: jolsa@xxxxxxxxxx
Link: http://lkml.kernel.org/r/1415156173-10035-7-git-send-email-kan.liang@xxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
kernel/events/core.c | 3 +++
1 file changed, 3 insertions(+)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 688086b..84451c0 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -2562,6 +2562,9 @@ static void perf_event_context_sched_out(struct task_struct *task, int ctxn,
next->perf_event_ctxp[ctxn] = ctx;
ctx->task = next;
next_ctx->task = task;
+ swap(ctx->task_ctx_data, next_ctx->task_ctx_data);
do_switch = 0;

perf_event_sync_stat(ctx, next_ctx);
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