perf: Fix perf_event_comm() vs. exec() assumption

perf_event_comm() assumes that set_task_comm() is only called on
exec(), and in particular that its only called on current.

Neither are true, as Dave reported a WARN triggered by set_task_comm()
being called on !current.

Separate the exec() hook from the comm hook.

Reported-by: Dave Jones <davej@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-fsdevel@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Link: http://lkml.kernel.org/r/20140521153219.GH5226@laptop.programming.kicks-ass.net
[ Build fix. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 3 insertions, 1 deletions

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 3ef6ea12806a..9b5cd1992a88 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -695,6 +695,7 @@ extern struct perf_guest_info_callbacks *perf_guest_cbs;
 extern int perf_register_guest_info_callbacks(struct perf_guest_info_callbacks *callbacks);
 extern int perf_unregister_guest_info_callbacks(struct perf_guest_info_callbacks *callbacks);
 
+extern void perf_event_exec(void);
 extern void perf_event_comm(struct task_struct *tsk);
 extern void perf_event_fork(struct task_struct *tsk);
 
@@ -772,7 +773,7 @@ extern void perf_event_enable(struct perf_event *event);
 extern void perf_event_disable(struct perf_event *event);
 extern int __perf_event_disable(void *info);
 extern void perf_event_task_tick(void);
-#else
+#else /* !CONFIG_PERF_EVENTS: */
 static inline void
 perf_event_task_sched_in(struct task_struct *prev,
                          struct task_struct *task)                      { }
@@ -802,6 +803,7 @@ static inline int perf_unregister_guest_info_callbacks
 (struct perf_guest_info_callbacks *callbacks)                           { return 0; }
 
 static inline void perf_event_mmap(struct vm_area_struct *vma)          { }
+static inline void perf_event_exec(void)                                { }
 static inline void perf_event_comm(struct task_struct *tsk)             { }
 static inline void perf_event_fork(struct task_struct *tsk)             { }
 static inline void perf_event_init(void)                                { }