[PATCH 2/2] perf: fixperf_event_init_task()/perf_event_free_task() interaction

[Oleg Nesterov]

perf_event_init_task() should clear child->perf_event_ctxp[] before
anything else. Otherwise, if perf_event_init_context(perf_hw_context)
fails, perf_event_free_task() can free perf_event_ctxp[perf_sw_context]
copied from parent->perf_event_ctxp[] by dup_task_struct().

Also move the initialization of perf_event_mutex and perf_event_list
from perf_event_init_context() to perf_event_init_context().

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
---

 kernel/perf_event.c |    9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

--- git/kernel/perf_event.c~4_perf_event_init_task	2011-01-19 17:41:16.000000000 +0100
+++ git/kernel/perf_event.c	2011-01-19 18:49:23.000000000 +0100
@@ -6446,11 +6446,6 @@ int perf_event_init_context(struct task_
 	unsigned long flags;
 	int ret = 0;
 
-	child->perf_event_ctxp[ctxn] = NULL;
-
-	mutex_init(&child->perf_event_mutex);
-	INIT_LIST_HEAD(&child->perf_event_list);
-
 	if (likely(!parent->perf_event_ctxp[ctxn]))
 		return 0;
 
@@ -6540,6 +6535,10 @@ int perf_event_init_task(struct task_str
 {
 	int ctxn, ret;
 
+	memset(child->perf_event_ctxp, 0, sizeof(child->perf_event_ctxp));
+	mutex_init(&child->perf_event_mutex);
+	INIT_LIST_HEAD(&child->perf_event_list);
+
 	for_each_task_context_nr(ctxn) {
 		ret = perf_event_init_context(child, ctxn);
 		if (ret)

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/