[PATCH v3 10/12] perf, persistent: Implement reference counter for events

[Robert Richter]

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

We need this later for proper event removal.

Signed-off-by: Robert Richter <robert.rich...@linaro.org>
Signed-off-by: Robert Richter <r...@kernel.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 f23270b..70446ae 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 @@ static int persistent_event_open(int cpu, struct pevent 
*pevent,
 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;
 }
-- 
1.8.3.2

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