[tip:perfcounters/core] perf_counter: Annotate exit ctx recursion

tip-bot for Peter Zijlstra
2009-06-11T00:43:36Z

Commit-ID: 66fff22483d8542dfb4d61a28d21277bbde321e8
Gitweb: http://git.kernel.org/tip/66fff22483d8542dfb4d61a28d21277bbde321e8
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Wed, 10 Jun 2009 22:53:37 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Thu, 11 Jun 2009 02:39:01 +0200

perf_counter: Annotate exit ctx recursion

Ever since Paul fixed it to unclone the context before taking the
ctx->lock this became a false positive, annotate it away.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

---
kernel/perf_counter.c | 13 ++++++++++++-
1 files changed, 12 insertions(+), 1 deletions(-)

diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 51c571e..ae591a1 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -3879,7 +3879,18 @@ void perf_counter_exit_task(struct task_struct *child)
spin_unlock(&child_ctx->lock);
local_irq_restore(flags);

- mutex_lock(&child_ctx->mutex);
+ /*
+ * We can recurse on the same lock type through:
+ *
+ * __perf_counter_exit_task()
+ * sync_child_counter()
+ * fput(parent_counter->filp)
+ * perf_release()
+ * mutex_lock(&ctx->mutex)
+ *
+ * But since its the parent context it won't be the same instance.
+ */
+ mutex_lock_nested(&child_ctx->mutex, SINGLE_DEPTH_NESTING);

again:
list_for_each_entry_safe(child_counter, tmp, &child_ctx->counter_list,