[PATCH 10/16] perf, persistent: Implement reference counter for events

Jean Pihet
2014-04-07T15:08:27Z

From: Robert Richter <robert.richter@linaro.org>

We need this later for proper event removal.

Signed-off-by: Robert Richter <robert.richter@linaro.org>
Signed-off-by: Robert Richter <rric@kernel.org>
Signed-off-by: Jean Pihet <jean.pihet@linaro.org>
---
kernel/events/persistent.c | 27 +++++++++++++++++----------
1 file changed, 17 insertions(+), 10 deletions(-)

diff --git a/kernel/events/persistent.c b/kernel/events/persistent.c
index d04827c..fcbb4f8 100644
--- a/kernel/events/persistent.c
+++ b/kernel/events/persistent.c
@@ -9,6 +9,7 @@
#define CPU_BUFFER_NR_PAGES ((512 * 1024) / PAGE_SIZE)

struct pevent {
+ atomic_t refcount;
struct perf_pmu_events_attr sysfs;
char *name;
int id;
@@ -130,6 +131,7 @@ static int persistent_event_open(int cpu, struct pevent *pevent,
if (ret)
goto fail;

+ atomic_inc(&pevent->refcount);
atomic_inc(&event->mmap_count);

/* All workie, enable event now */
@@ -144,8 +146,11 @@ fail:
static void persistent_event_close(int cpu, struct pevent *pevent)
{
struct perf_event *event = pevent_del(pevent, cpu);
- if (event)
+ if (event) {
+ /* Safe, the caller holds &pevent->refcount too. */
+ atomic_dec(&pevent->refcount);
persistent_event_release(event);
+ }
}

static int pevent_sysfs_register(struct pevent *event);
@@ -162,6 +167,8 @@ persistent_open(char *name, struct perf_event_attr *attr, int nr_pages)
if (!pevent)
return -ENOMEM;

+ atomic_set(&pevent->refcount, 1);
+
ret = get_event_id(pevent);
if (ret < 0)
goto fail;
@@ -187,21 +194,21 @@ persistent_open(char *name, struct perf_event_attr *attr, int nr_pages)
}

ret = pevent_sysfs_register(pevent);
- if (ret)
- goto fail;
-
- return 0;
+ if (!ret)
+ goto out;
fail:
for_each_possible_cpu(cpu)
persistent_event_close(cpu, pevent);

- if (pevent->id)
- put_event_id(pevent->id);
- kfree(pevent->name);
- kfree(pevent);
-
pr_err("%s: Error adding persistent event: %d\n",
__func__, ret);
+out:
+ if (atomic_dec_and_test(&pevent->refcount)) {
+ if (pevent->id)
+ put_event_id(pevent->id);
+ kfree(pevent->name);
+ kfree(pevent);
+ }

return ret;
}
--
1.7.11.7