From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Fri, 15 May 2009 18:45:59 +0000 (+0200)
Subject: perf_counter: Fix counter inheritance
X-Git-Tag: v2.6.31-rc1~383^2~261
X-Git-Url: https://openfabrics.org/gitweb/?a=commitdiff_plain;h=856d56b9e5de650a64a6c41c17aaed702b55d578;p=~emulex%2Finfiniband.git

perf_counter: Fix counter inheritance

Srivatsa Vaddagiri reported that a Java workload triggers this
warning in kernel/exit.c:

   WARN_ON_ONCE(!list_empty(&tsk->perf_counter_ctx.counter_list));

Add the inherited counter propagation on self-detach, this could
cause counter leaks and incomplete stats in threaded code like
the below:

  #include <pthread.h>
  #include <unistd.h>

  void *thread(void *arg)
  {
          sleep(5);
          return NULL;
  }

  void main(void)
  {
          pthread_t thr;
          pthread_create(&thr, NULL, thread, NULL);
  }

Reported-by: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

diff --git a/kernel/exit.c b/kernel/exit.c
index 4741376c8de..16d74f13a3e 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -128,6 +128,12 @@ static void __exit_signal(struct task_struct *tsk)
 		sig = NULL; /* Marker for below. */
 	}
 
+	/*
+	 * Flush inherited counters to the parent - before the parent
+	 * gets woken up by child-exit notifications.
+	 */
+	perf_counter_exit_task(tsk);
+
 	__unhash_process(tsk);
 
 	/*