perf top: Access hists->lock only if needed

The perf_top__record_precise_ip() releases and regrabs the
he->hists->lock because it can sleep if there's an error.  But it should
be done conditionally as it slows down the fast path.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1449802616-16170-2-git-send-email-namhyung@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 15 insertions, 13 deletions

diff --git a/tools/perf/builtin-top.c b/tools/perf/builtin-top.c
index 3b0978e5578a..586798acf7db 100644
--- a/tools/perf/builtin-top.c
+++ b/tools/perf/builtin-top.c
@@ -194,21 +194,23 @@ static void perf_top__record_precise_ip(struct perf_top *top,
 
         pthread_mutex_unlock(&notes->lock);
 
-        /*
-         * This function is now called with he->hists->lock held.
-         * Release it before going to sleep.
-         */
-        pthread_mutex_unlock(&he->hists->lock);
+        if (unlikely(err)) {
+                /*
+                 * This function is now called with he->hists->lock held.
+                 * Release it before going to sleep.
+                 */
+                pthread_mutex_unlock(&he->hists->lock);
+
+                if (err == -ERANGE && !he->ms.map->erange_warned)
+                        ui__warn_map_erange(he->ms.map, sym, ip);
+                else if (err == -ENOMEM) {
+                        pr_err("Not enough memory for annotating '%s' symbol!\n",
+                               sym->name);
+                        sleep(1);
+                }
 
-        if (err == -ERANGE && !he->ms.map->erange_warned)
-                ui__warn_map_erange(he->ms.map, sym, ip);
-        else if (err == -ENOMEM) {
-                pr_err("Not enough memory for annotating '%s' symbol!\n",
-                       sym->name);
-                sleep(1);
+                pthread_mutex_lock(&he->hists->lock);
         }
-
-        pthread_mutex_lock(&he->hists->lock);
 }
 
 static void perf_top__show_details(struct perf_top *top)