[PATCH 1/2] perf: Avoid overwriting precise timestamp

[Kan Liang]

Signed-off-by: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
---
 arch/x86/events/intel/ds.c | 8 ++++++--
 include/linux/perf_event.h | 3 +++
 kernel/events/core.c       | 2 +-
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/arch/x86/events/intel/ds.c b/arch/x86/events/intel/ds.c
index 34be3bc5151a..a2c26eaeb0d9 100644
--- a/arch/x86/events/intel/ds.c
+++ b/arch/x86/events/intel/ds.c
@@ -1687,8 +1687,10 @@ static void setup_pebs_fixed_sample_data(struct
perf_event *event,
 	 * We can only do this for the default trace clock.
 	 */
 	if (x86_pmu.intel_cap.pebs_format >= 3 &&
-		event->attr.use_clockid == 0)
+		event->attr.use_clockid == 0) {
 		data->time = native_sched_clock_from_tsc(pebs->tsc);
+		data->flags |= PERF_SAMPLE_DATA_TIME;
+	}

 	if (has_branch_stack(event))
 		data->br_stack = &cpuc->lbr_stack;
@@ -1750,8 +1752,10 @@ static void
setup_pebs_adaptive_sample_data(struct perf_event *event,
 	perf_sample_data_init(data, 0, event->hw.last_period);
 	data->period = event->hw.last_period;

-	if (event->attr.use_clockid == 0)
+	if (event->attr.use_clockid == 0) {
 		data->time = native_sched_clock_from_tsc(basic->tsc);
+		data->flags |= PERF_SAMPLE_DATA_TIME;
+	}

 	/*
 	 * We must however always use iregs for the unwinder to stay sane; the
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index da759560eec5..33054bf31fc1 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -999,6 +999,7 @@ int perf_event_read_local(struct perf_event *event,
u64 *value,
 extern u64 perf_event_read_value(struct perf_event *event,
 				 u64 *enabled, u64 *running);

+#define PERF_SAMPLE_DATA_TIME		0x1

 struct perf_sample_data {
 	/*
@@ -1012,6 +1013,7 @@ struct perf_sample_data {
 	union perf_sample_weight	weight;
 	u64				txn;
 	union  perf_mem_data_src	data_src;
+	u64				flags;

 	/*
 	 * The other fields, optionally {set,used} by
@@ -1061,6 +1063,7 @@ static inline void perf_sample_data_init(struct
perf_sample_data *data,
 	data->weight.full = 0;
 	data->data_src.val = PERF_MEM_NA;
 	data->txn = 0;
+	data->flags = 0;
 }

 /*
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 65e0bcba2e21..057c197ae106 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6799,7 +6799,7 @@ static void __perf_event_header__init_id(struct
perf_event_header *header,
 		data->tid_entry.tid = perf_event_tid(event, current);
 	}

-	if (sample_type & PERF_SAMPLE_TIME)
+	if ((sample_type & PERF_SAMPLE_TIME) && !(data->flags &
PERF_SAMPLE_DATA_TIME))
 		data->time = perf_event_clock(event);

 	if (sample_type & (PERF_SAMPLE_ID | PERF_SAMPLE_IDENTIFIER))
-- 
2.35.1




The patch as below use a new flag to track the availability of the br_stack.