[PATCH v2 4/5] perf/x86/intel/pt: Move transaction start/stop to pmu start/stop callbacks

Alexander Shishkin
2016-03-04T13:43:49Z

As per AUX buffer management requirement, AUX output has to happen between
pmu::start and pmu::stop calls so that perf_event_stop() actually stops it
and therefore perf can free the aux data after it has called pmu::stop.

This patch moves perf_aux_output_{begin,end} from pt_event_{add,del} to
pt_event_{start,stop}. As a bonus, we get rid of pt_buffer_is_full(),
which is already taken care of by perf_aux_output_begin() anyway.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
---
arch/x86/events/intel/pt.c | 85 +++++++++++++++-------------------------------
1 file changed, 27 insertions(+), 58 deletions(-)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index 6af7cf71d6..127f58c179 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -906,26 +906,6 @@ static void pt_buffer_free_aux(void *data)
}

/**
- * pt_buffer_is_full() - check if the buffer is full
- * @buf: PT buffer.
- * @pt: Per-cpu pt handle.
- *
- * If the user hasn't read data from the output region that aux_head
- * points to, the buffer is considered full: the user needs to read at
- * least this region and update aux_tail to point past it.
- */
-static bool pt_buffer_is_full(struct pt_buffer *buf, struct pt *pt)
-{
- if (buf->snapshot)
- return false;
-
- if (local_read(&buf->data_size) >= pt->handle.size)
- return true;
-
- return false;
-}
-
-/**
* intel_pt_interrupt() - PT PMI handler
*/
void intel_pt_interrupt(void)
@@ -989,20 +969,33 @@ void intel_pt_interrupt(void)

static void pt_event_start(struct perf_event *event, int mode)
{
+ struct hw_perf_event *hwc = &event->hw;
struct pt *pt = this_cpu_ptr(&pt_ctx);
- struct pt_buffer *buf = perf_get_aux(&pt->handle);
+ struct pt_buffer *buf;

- if (!buf || pt_buffer_is_full(buf, pt)) {
- event->hw.state = PERF_HES_STOPPED;
- return;
+ buf = perf_aux_output_begin(&pt->handle, event);
+ if (!buf)
+ goto fail_stop;
+
+ pt_buffer_reset_offsets(buf, pt->handle.head);
+ if (!buf->snapshot) {
+ if (pt_buffer_reset_markers(buf, &pt->handle))
+ goto fail_end_stop;
}

ACCESS_ONCE(pt->handle_nmi) = 1;
- event->hw.state = 0;
+ hwc->state = 0;

pt_config_buffer(buf->cur->table, buf->cur_idx,
buf->output_off);
pt_config(event);
+
+ return;
+
+fail_end_stop:
+ perf_aux_output_end(&pt->handle, 0, true);
+fail_stop:
+ hwc->state = PERF_HES_STOPPED;
}

static void pt_event_stop(struct perf_event *event, int mode)
@@ -1035,19 +1028,7 @@ static void pt_event_stop(struct perf_event *event, int mode)
pt_handle_status(pt);

pt_update_head(pt);
- }
-}

-static void pt_event_del(struct perf_event *event, int mode)
-{
- struct pt *pt = this_cpu_ptr(&pt_ctx);
- struct pt_buffer *buf;
-
- pt_event_stop(event, PERF_EF_UPDATE);
-
- buf = perf_get_aux(&pt->handle);
-
- if (buf) {
if (buf->snapshot)
pt->handle.head =
local_xchg(&buf->data_size,
@@ -1057,9 +1038,13 @@ static void pt_event_del(struct perf_event *event, int mode)
}
}

+static void pt_event_del(struct perf_event *event, int mode)
+{
+ pt_event_stop(event, PERF_EF_UPDATE);
+}
+
static int pt_event_add(struct perf_event *event, int mode)
{
- struct pt_buffer *buf;
struct pt *pt = this_cpu_ptr(&pt_ctx);
struct hw_perf_event *hwc = &event->hw;
int ret = -EBUSY;
@@ -1067,34 +1052,18 @@ static int pt_event_add(struct perf_event *event, int mode)
if (pt->handle.event)
goto fail;

- buf = perf_aux_output_begin(&pt->handle, event);
- ret = -EINVAL;
- if (!buf)
- goto fail_stop;
-
- pt_buffer_reset_offsets(buf, pt->handle.head);
- if (!buf->snapshot) {
- ret = pt_buffer_reset_markers(buf, &pt->handle);
- if (ret)
- goto fail_end_stop;
- }
-
if (mode & PERF_EF_START) {
pt_event_start(event, 0);
- ret = -EBUSY;
+ ret = -EINVAL;
if (hwc->state == PERF_HES_STOPPED)
- goto fail_end_stop;
+ goto fail;
} else {
hwc->state = PERF_HES_STOPPED;
}

- return 0;
-
-fail_end_stop:
- perf_aux_output_end(&pt->handle, 0, true);
-fail_stop:
- hwc->state = PERF_HES_STOPPED;
+ ret = 0;
fail:
+
return ret;
}

--
2.7.0