Messages in this thread | | | Date | Tue, 9 Nov 2010 19:57:48 +0100 | From | Oleg Nesterov <> | Subject | Re: Q: perf_event && event->owner |
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On 11/09, Peter Zijlstra wrote: > > I think you're right, how about something like this?
I need to read it with a fresh head ;)
At first glance,
> @@ -2254,6 +2249,12 @@ static int perf_release(struct inode *in > > file->private_data = NULL; > > + if (event->owner) { > + mutex_lock(&event->owner->perf_event_mutex); > + list_del_init(&event->owner_entry); > + mutex_unlock(&event->owner->perf_event_mutex); > + }
Agreed, it is better to do this in perf_release().
But, this can use the already freed task_struct, event->owner.
Either sys_perf_open() should do get_task_struct() like we currently do, or perf_event_exit_task() should clear event->owner and then perf_release() should do something like
rcu_read_lock(); owner = event->owner; if (owner) get_task_struct(owner); rcu_read_unlock();
if (owner) { mutex_lock(&event->owner->perf_event_mutex); list_del_init(&event->owner_entry); mutex_unlock(&event->owner->perf_event_mutex); put_task_struct(owner); }
Probably this can be simplified...
Oleg.
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