perf_counter: Full task tracing

In order to be able to distinguish between no samples due to
inactivity and no samples due to task ended, Arjan asked for
PERF_EVENT_EXIT events. This is useful to the boot delay
instrumentation (bootchart) app.

This patch changes the PERF_EVENT_FORK to be emitted on every
clone, and adds PERF_EVENT_EXIT to be emitted on task exit,
after the task's counters have been closed.

This task tracing is controlled through: attr.comm || attr.mmap
and through the new attr.task field.

Suggested-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Anton Blanchard <anton@samba.org>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
[ cleaned up perf_counter.h a bit ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 1 insertions, 3 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index 29b532e718f7..466531eb92cc 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -1269,6 +1269,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
         write_unlock_irq(&tasklist_lock);
         proc_fork_connector(p);
         cgroup_post_fork(p);
+        perf_counter_fork(p);
         return p;
 
 bad_fork_free_pid:
@@ -1410,9 +1411,6 @@ long do_fork(unsigned long clone_flags,
                         init_completion(&vfork);
                 }
 
-                if (!(clone_flags & CLONE_THREAD))
-                        perf_counter_fork(p);
-
                 audit_finish_fork(p);
                 tracehook_report_clone(regs, clone_flags, nr, p);