perf: fix perf_event_context->time

[ Upstream commit baf1b12a67f5b24f395baca03e442ce27cab0c18 ]

Time readers rely on perf_event_context->[time|timestamp|timeoffset] to get
accurate time_enabled and time_running for an event. The difference between
ctx->timestamp and ctx->time is the among of time when the context is not
enabled. __update_context_time(ctx, false) is used to increase timestamp,
but not time. Therefore, it should only be called in ctx_sched_in() when
EVENT_TIME was not enabled.

Fixes: 09f5e7dc7ad7 ("perf: Fix perf_event_read_local() time")
Signed-off-by: Song Liu <song@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/r/20230313171608.298734-1-song@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6c4e78c..2aa286b 100644 (file)
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3830,7 +3830,7 @@ ctx_sched_in(struct perf_event_context *ctx,
        if (likely(!ctx->nr_events))
                return;
 
-       if (is_active ^ EVENT_TIME) {
+       if (!(is_active & EVENT_TIME)) {
                /* start ctx time */
                __update_context_time(ctx, false);
                perf_cgroup_set_timestamp(cpuctx);