From dc633982ff3f4fd74cdc11b5a6ae53d39a0b2451 Mon Sep 17 00:00:00 2001 From: Jiri Olsa Date: Fri, 12 Sep 2014 13:18:26 +0200 Subject: [PATCH] perf: Do not POLLHUP event if it has children Currently we return POLLHUP in event polling if the monitored process is done, but we didn't consider possible children, that might be still running and producing data. Before returning POLLHUP making sure that: 1) the monitored task has exited and that 2) we don't have any children to monitor Also adding parent wakeup when the child event is gone. Suggested-by: Peter Zijlstra Signed-off-by: Jiri Olsa Signed-off-by: Peter Zijlstra (Intel) Link: http://lkml.kernel.org/r/1410520708-19275-1-git-send-email-jolsa@kernel.org Cc: Arnaldo Carvalho de Melo Cc: Frederic Weisbecker Cc: Paul Mackerras Cc: Stephane Eranian Cc: Arnaldo Carvalho de Melo Cc: Frederic Weisbecker Cc: Paul Mackerras Cc: Stephane Eranian Cc: Linus Torvalds Signed-off-by: Ingo Molnar --- kernel/events/core.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index 733c61636f0d..15e58d4ea035 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3587,6 +3587,19 @@ static int perf_event_read_one(struct perf_event *event, return n * sizeof(u64); } +static bool is_event_hup(struct perf_event *event) +{ + bool no_children; + + if (event->state != PERF_EVENT_STATE_EXIT) + return false; + + mutex_lock(&event->child_mutex); + no_children = list_empty(&event->child_list); + mutex_unlock(&event->child_mutex); + return no_children; +} + /* * Read the performance event - simple non blocking version for now */ @@ -3632,7 +3645,7 @@ static unsigned int perf_poll(struct file *file, poll_table *wait) poll_wait(file, &event->waitq, wait); - if (event->state == PERF_EVENT_STATE_EXIT) + if (is_event_hup(event)) return events; /* @@ -7579,6 +7592,12 @@ static void sync_child_event(struct perf_event *child_event, list_del_init(&child_event->child_list); mutex_unlock(&parent_event->child_mutex); + /* + * Make sure user/parent get notified, that we just + * lost one event. + */ + perf_event_wakeup(parent_event); + /* * Release the parent event, if this was the last * reference to it. -- 2.20.1