perf evlist: Clarify a bit the use of perf_mmap->refcnt

[karo-tx-linux.git] / tools / perf / util / evlist.c

diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
index b601f2814a30e9d7d2b6f689b5e495659c34e600..50420cd354467361615d8606d6dde73f5e588a45 100644 (file)
--- a/tools/perf/util/evlist.c
+++ b/tools/perf/util/evlist.c
@@ -777,7 +777,7 @@ union perf_event *perf_mmap__read_forward(struct perf_mmap *md, bool check_messu
        /*
         * Check if event was unmapped due to a POLLHUP/POLLERR.
         */
-       if (!atomic_read(&md->refcnt))
+       if (!refcount_read(&md->refcnt))
                return NULL;
 
        head = perf_mmap__read_head(md);
@@ -794,7 +794,7 @@ perf_mmap__read_backward(struct perf_mmap *md)
        /*
         * Check if event was unmapped due to a POLLHUP/POLLERR.
         */
-       if (!atomic_read(&md->refcnt))
+       if (!refcount_read(&md->refcnt))
                return NULL;
 
        head = perf_mmap__read_head(md);
@@ -856,7 +856,7 @@ void perf_mmap__read_catchup(struct perf_mmap *md)
 {
        u64 head;
 
-       if (!atomic_read(&md->refcnt))
+       if (!refcount_read(&md->refcnt))
                return;
 
        head = perf_mmap__read_head(md);
@@ -875,14 +875,14 @@ static bool perf_mmap__empty(struct perf_mmap *md)
 
 static void perf_mmap__get(struct perf_mmap *map)
 {
-       atomic_inc(&map->refcnt);
+       refcount_inc(&map->refcnt);
 }
 
 static void perf_mmap__put(struct perf_mmap *md)
 {
-       BUG_ON(md->base && atomic_read(&md->refcnt) == 0);
+       BUG_ON(md->base && refcount_read(&md->refcnt) == 0);
 
-       if (atomic_dec_and_test(&md->refcnt))
+       if (refcount_dec_and_test(&md->refcnt))
                perf_mmap__munmap(md);
 }
 
@@ -894,7 +894,7 @@ void perf_mmap__consume(struct perf_mmap *md, bool overwrite)
                perf_mmap__write_tail(md, old);
        }
 
-       if (atomic_read(&md->refcnt) == 1 && perf_mmap__empty(md))
+       if (refcount_read(&md->refcnt) == 1 && perf_mmap__empty(md))
                perf_mmap__put(md);
 }
 
@@ -937,7 +937,7 @@ static void perf_mmap__munmap(struct perf_mmap *map)
                munmap(map->base, perf_mmap__mmap_len(map));
                map->base = NULL;
                map->fd = -1;
-               atomic_set(&map->refcnt, 0);
+               refcount_set(&map->refcnt, 0);
        }
        auxtrace_mmap__munmap(&map->auxtrace_mmap);
 }
@@ -974,8 +974,19 @@ static struct perf_mmap *perf_evlist__alloc_mmap(struct perf_evlist *evlist)
        if (!map)
                return NULL;
 
-       for (i = 0; i < evlist->nr_mmaps; i++)
+       for (i = 0; i < evlist->nr_mmaps; i++) {
                map[i].fd = -1;
+               /*
+                * When the perf_mmap() call is made we grab one refcount, plus
+                * one extra to let perf_evlist__mmap_consume() get the last
+                * events after all real references (perf_mmap__get()) are
+                * dropped.
+                *
+                * Each PERF_EVENT_IOC_SET_OUTPUT points to this mmap and
+                * thus does perf_mmap__get() on it.
+                */
+               refcount_set(&map[i].refcnt, 0);
+       }
        return map;
 }
 
@@ -1001,7 +1012,7 @@ static int perf_mmap__mmap(struct perf_mmap *map,
         * evlist layer can't just drop it when filtering events in
         * perf_evlist__filter_pollfd().
         */
-       atomic_set(&map->refcnt, 2);
+       refcount_set(&map->refcnt, 2);
        map->prev = 0;
        map->mask = mp->mask;
        map->base = mmap(NULL, perf_mmap__mmap_len(map), mp->prot,