[PATCH 2/3] perf/x86/intel/pt: Use bitwise access for PERF_HES_STOPPED

[Adrian Hunter]

The Intel PT driver reads and writes event->hw.state as a whole value,
assuming it is either 0 or PERF_HES_STOPPED.  That is true today, but a
subsequent fix needs to also track an open AUX output buffer using the
PERF_HES_UPTODATE bit of the same field.

When more than one bit can be set, whole-value assignments would
overwrite the other bits and whole-value comparisons would fail to match.

Convert all accesses to set, clear and test the PERF_HES_STOPPED bit
individually, in preparation for that change.

No functional change intended: event->hw.state currently only ever
holds 0 or PERF_HES_STOPPED, so the bitwise forms are equivalent.

Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
---
 arch/x86/events/intel/pt.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index dc1be7f6e04b..2163e5ccdc04 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -1540,12 +1540,12 @@ void intel_pt_interrupt(void)
 
 	perf_aux_output_end(&pt->handle, local_xchg(&buf->data_size, 0));
 
-	if (!event->hw.state) {
+	if (!(event->hw.state & PERF_HES_STOPPED)) {
 		int ret;
 
 		buf = perf_aux_output_begin(&pt->handle, event);
 		if (!buf) {
-			event->hw.state = PERF_HES_STOPPED;
+			event->hw.state |= PERF_HES_STOPPED;
 			WRITE_ONCE(pt->resume_allowed, 0);
 			return;
 		}
@@ -1639,7 +1639,7 @@ static void pt_event_start(struct perf_event *event, int mode)
 			goto fail_end_stop;
 	}
 
-	hwc->state = 0;
+	hwc->state &= ~PERF_HES_STOPPED;
 
 	pt_config_buffer(buf);
 	pt_config(event);
@@ -1649,7 +1649,7 @@ static void pt_event_start(struct perf_event *event, int mode)
 fail_end_stop:
 	perf_aux_output_end(&pt->handle, 0);
 fail_stop:
-	hwc->state = PERF_HES_STOPPED;
+	hwc->state |= PERF_HES_STOPPED;
 }
 
 static void pt_event_stop(struct perf_event *event, int mode)
@@ -1680,10 +1680,10 @@ static void pt_event_stop(struct perf_event *event, int mode)
 
 	pt_config_stop(event);
 
-	if (event->hw.state == PERF_HES_STOPPED)
+	if (event->hw.state & PERF_HES_STOPPED)
 		return;
 
-	event->hw.state = PERF_HES_STOPPED;
+	event->hw.state |= PERF_HES_STOPPED;
 
 	if (mode & PERF_EF_UPDATE) {
 		struct pt_buffer *buf = perf_get_aux(&pt->handle);
@@ -1778,10 +1778,10 @@ static int pt_event_add(struct perf_event *event, int mode)
 	if (mode & PERF_EF_START) {
 		pt_event_start(event, 0);
 		ret = -EINVAL;
-		if (hwc->state == PERF_HES_STOPPED)
+		if (hwc->state & PERF_HES_STOPPED)
 			goto fail;
 	} else {
-		hwc->state = PERF_HES_STOPPED;
+		hwc->state |= PERF_HES_STOPPED;
 	}
 
 	ret = 0;
-- 
2.53.0