perf unwind: Call unwind__prepare_access for forked thread

Currently we call unwind__prepare_access for map event.  In case we
report fork event the thread inherits its parent's maps and
unwind__prepare_access is never called for the thread.

This causes unwind__get_entries seeing uninitialized
unwind_libunwind_ops and thus returning no callchain.

Adding unwind__prepare_access calls for fork even processing.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: He Kuang <hekuang@huawei.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1467634583-29147-5-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

3 files changed, 44 insertions, 4 deletions

diff --git a/tools/perf/util/map.c b/tools/perf/util/map.c
index b19bcd3b7128..b39b12a1208d 100644
--- a/tools/perf/util/map.c
+++ b/tools/perf/util/map.c
@@ -15,6 +15,7 @@
 #include "debug.h"
 #include "machine.h"
 #include <linux/string.h>
+#include "unwind.h"
 
 static void __maps__insert(struct maps *maps, struct map *map);
 
@@ -744,9 +745,10 @@ int map_groups__fixup_overlappings(struct map_groups *mg, struct map *map,
 /*
  * XXX This should not really _copy_ te maps, but refcount them.
  */
-int map_groups__clone(struct map_groups *mg,
+int map_groups__clone(struct thread *thread,
                       struct map_groups *parent, enum map_type type)
 {
+        struct map_groups *mg = thread->mg;
         int err = -ENOMEM;
         struct map *map;
         struct maps *maps = &parent->maps[type];
@@ -757,6 +759,11 @@ int map_groups__clone(struct map_groups *mg,
                 struct map *new = map__clone(map);
                 if (new == NULL)
                         goto out_unlock;
+
+                err = unwind__prepare_access(thread, new, NULL);
+                if (err)
+                        goto out_unlock;
+
                 map_groups__insert(mg, new);
                 map__put(new);
         }
diff --git a/tools/perf/util/map.h b/tools/perf/util/map.h
index 7309d64ce39e..d83396ceecba 100644
--- a/tools/perf/util/map.h
+++ b/tools/perf/util/map.h
@@ -194,7 +194,7 @@ struct symbol *maps__find_symbol_by_name(struct maps *maps, const char *name,
                                          struct map **mapp, symbol_filter_t filter);
 void map_groups__init(struct map_groups *mg, struct machine *machine);
 void map_groups__exit(struct map_groups *mg);
-int map_groups__clone(struct map_groups *mg,
+int map_groups__clone(struct thread *thread,
                       struct map_groups *parent, enum map_type type);
 size_t map_groups__fprintf(struct map_groups *mg, FILE *fp);
 
diff --git a/tools/perf/util/thread.c b/tools/perf/util/thread.c
index 2439b122a4e4..8b10a55410a2 100644
--- a/tools/perf/util/thread.c
+++ b/tools/perf/util/thread.c
@@ -212,6 +212,39 @@ int thread__insert_map(struct thread *thread, struct map *map)
         return 0;
 }
 
+static int __thread__prepare_access(struct thread *thread)
+{
+        bool initialized = false;
+        int i, err = 0;
+
+        for (i = 0; i < MAP__NR_TYPES; ++i) {
+                struct maps *maps = &thread->mg->maps[i];
+                struct map *map;
+
+                pthread_rwlock_rdlock(&maps->lock);
+
+                for (map = maps__first(maps); map; map = map__next(map)) {
+                        err = unwind__prepare_access(thread, map, &initialized);
+                        if (err || initialized)
+                                break;
+                }
+
+                pthread_rwlock_unlock(&maps->lock);
+        }
+
+        return err;
+}
+
+static int thread__prepare_access(struct thread *thread)
+{
+        int err = 0;
+
+        if (symbol_conf.use_callchain)
+                err = __thread__prepare_access(thread);
+
+        return err;
+}
+
 static int thread__clone_map_groups(struct thread *thread,
                                     struct thread *parent)
 {
@@ -219,7 +252,7 @@ static int thread__clone_map_groups(struct thread *thread,
 
         /* This is new thread, we share map groups for process. */
         if (thread->pid_ == parent->pid_)
-                return 0;
+                return thread__prepare_access(thread);
 
         if (thread->mg == parent->mg) {
                 pr_debug("broken map groups on thread %d/%d parent %d/%d\n",
@@ -229,7 +262,7 @@ static int thread__clone_map_groups(struct thread *thread,
 
         /* But this one is new process, copy maps. */
         for (i = 0; i < MAP__NR_TYPES; ++i)
-                if (map_groups__clone(thread->mg, parent->mg, i) < 0)
+                if (map_groups__clone(thread, parent->mg, i) < 0)
                         return -ENOMEM;
 
         return 0;