[PATCH 3/5] perf: New PERF_EVENT_STATE_PAUSED event state

[Frederic Weisbecker]

This brings a new PERF_EVENT_STATE_PAUSED state. It means the events
is enabled but we don't want it to run, it must be in the same state
than after a pmu->stop() call. So the event has been reserved and
allocated and it is ready to start after a pmu->start() call.

It is deemed for hardware events when we want them to be reserved on
the cpu and ready to be started anytime. This is going to be useful
for the new context exclusion that will follow.

Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxx>
Cc: Zhang Yanmin <yanmin_zhang@xxxxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 arch/x86/kernel/cpu/perf_event.c |    6 ++++--
 include/linux/perf_event.h       |    3 ++-
 kernel/perf_event.c              |    7 ++++---
 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event.c b/arch/x86/kernel/cpu/perf_event.c
index f2da20f..9b0e52f 100644
--- a/arch/x86/kernel/cpu/perf_event.c
+++ b/arch/x86/kernel/cpu/perf_event.c
@@ -839,7 +839,8 @@ void hw_perf_enable(void)
 			    match_prev_assignment(hwc, cpuc, i))
 				continue;
 
-			x86_pmu_stop(event);
+			if (event->state != PERF_EVENT_STATE_PAUSED)
+				x86_pmu_stop(event);
 		}
 
 		for (i = 0; i < cpuc->n_events; i++) {
@@ -851,7 +852,8 @@ void hw_perf_enable(void)
 			else if (i < n_running)
 				continue;
 
-			x86_pmu_start(event);
+			if (event->state != PERF_EVENT_STATE_PAUSED)
+				x86_pmu_start(event);
 		}
 		cpuc->n_added = 0;
 		perf_events_lapic_init();
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 63b5aa5..48b3157 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -598,7 +598,8 @@ enum perf_event_active_state {
 	PERF_EVENT_STATE_ERROR		= -2,
 	PERF_EVENT_STATE_OFF		= -1,
 	PERF_EVENT_STATE_INACTIVE	=  0,
-	PERF_EVENT_STATE_ACTIVE		=  1,
+	PERF_EVENT_STATE_PAUSED		=  1,
+	PERF_EVENT_STATE_ACTIVE		=  2,
 };
 
 struct file;
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index 2d818bc..7c6502a 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -1541,20 +1541,21 @@ static void perf_adjust_period(struct perf_event *event, u64 nsec, u64 count)
 	hwc->sample_period = sample_period;
 
 	if (local64_read(&hwc->period_left) > 8*sample_period) {
-		bool software_event = is_software_event(event);
+		bool reprogram = !is_software_event(event) &&
+				 event->state != PERF_EVENT_STATE_PAUSED;
 
 		/*
 		 * Only hardware events need their irq period to be
 		 * reprogrammed
 		 */
-		if (!software_event) {
+		if (reprogram) {
 			perf_disable();
 			perf_event_stop(event);
 		}
 
 		local64_set(&hwc->period_left, 0);
 
-		if (!software_event) {
+		if (reprogram) {
 			perf_event_start(event);
 			perf_enable();
 		}
-- 
1.6.2.3

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