From: Jiri Olsa <[email protected]> When task exits we close: 1) all events that are installed in task 2) all events owned by task (via file descriptor)
But we don't close children events of 2) events. Those children events stay until the child task exits and are useless with the parent being gone, because we have no way to get to values any more. Plus if the event stays installed in task even with the owner task gone, it runs the perf callback any time the task forks, for no real reason. Closing all children events events when the owner task of the parent event is closed. Cc: Alexander Yarygin <[email protected]> Cc: Arnaldo Carvalho de Melo <[email protected]> Cc: Corey Ashford <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Paul Mackerras <[email protected]> Cc: Peter Zijlstra <[email protected]> Signed-off-by: Jiri Olsa <[email protected]> --- kernel/events/core.c | 27 +++++++++++++++++++++++++++ 1 file changed, 27 insertions(+) diff --git a/kernel/events/core.c b/kernel/events/core.c index 71a56ae..37797dd 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7535,6 +7535,32 @@ static void perf_event_exit_task_context(struct task_struct *child, int ctxn) put_ctx(child_ctx); } +static void perf_event_exit_children(struct perf_event *parent) +{ + struct perf_event *child, *tmp; + + mutex_lock(&parent->child_mutex); + list_for_each_entry_safe(child, tmp, &parent->child_list, + child_list) { + struct perf_event_context *child_ctx = child->ctx; + + /* + * Child events got removed from child_list under + * child_mutex and then freed. So it's safe to access + * childs context in here, because the child holds + * context ref. + */ + mutex_lock(&child_ctx->mutex); + perf_remove_from_context(child, true); + mutex_unlock(&child_ctx->mutex); + + list_del_init(&child->child_list); + put_event(parent); + free_event(child); + } + mutex_unlock(&parent->child_mutex); +} + /* * When a child task exits, feed back event values to parent events. */ @@ -7555,6 +7581,7 @@ void perf_event_exit_task(struct task_struct *child) */ smp_wmb(); event->owner = NULL; + perf_event_exit_children(event); } mutex_unlock(&child->perf_event_mutex); -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
