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@intel.com>
Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: eranian@google.com
Cc: jolsa@redhat.com
Link: http://lkml.kernel.org/r/1415156173-10035-7-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 688086bb7144200b20e6a4ba9c9e94e9c4955d74..84451c0debbacc8c85cd4c2045ce7b62a1c384f0 100644 (file)
--- 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);