perf_counter: Fix ctx->mutex vs counter->mutex inversion
Simon triggered a lockdep inversion report about us taking ctx->mutex
vs counter->mutex in inverse orders. Fix that up.
Reported-by: Simon Holm Thøgersen <odie@cs.aau.dk>
Tested-by: Simon Holm Thøgersen <odie@cs.aau.dk>
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>
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index e914daf..109a957 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1620,22 +1620,6 @@
perf_counter_update_userpage(counter);
}
-static void perf_counter_for_each_sibling(struct perf_counter *counter,
- void (*func)(struct perf_counter *))
-{
- struct perf_counter_context *ctx = counter->ctx;
- struct perf_counter *sibling;
-
- WARN_ON_ONCE(ctx->parent_ctx);
- mutex_lock(&ctx->mutex);
- counter = counter->group_leader;
-
- func(counter);
- list_for_each_entry(sibling, &counter->sibling_list, list_entry)
- func(sibling);
- mutex_unlock(&ctx->mutex);
-}
-
/*
* Holding the top-level counter's child_mutex means that any
* descendant process that has inherited this counter will block
@@ -1658,14 +1642,18 @@
static void perf_counter_for_each(struct perf_counter *counter,
void (*func)(struct perf_counter *))
{
- struct perf_counter *child;
+ struct perf_counter_context *ctx = counter->ctx;
+ struct perf_counter *sibling;
- WARN_ON_ONCE(counter->ctx->parent_ctx);
- mutex_lock(&counter->child_mutex);
- perf_counter_for_each_sibling(counter, func);
- list_for_each_entry(child, &counter->child_list, child_list)
- perf_counter_for_each_sibling(child, func);
- mutex_unlock(&counter->child_mutex);
+ WARN_ON_ONCE(ctx->parent_ctx);
+ mutex_lock(&ctx->mutex);
+ counter = counter->group_leader;
+
+ perf_counter_for_each_child(counter, func);
+ func(counter);
+ list_for_each_entry(sibling, &counter->sibling_list, list_entry)
+ perf_counter_for_each_child(counter, func);
+ mutex_unlock(&ctx->mutex);
}
static int perf_counter_period(struct perf_counter *counter, u64 __user *arg)