perf: Add PERF_EVENT_STATE_EXIT state for events with exited task
Adding new perf event state to indicate that the monitored task has
exited. In this case the event stays alive until the owner task exits
or close the event fd while providing the last data through the read
syscall and ring buffer.
Instead it needs to propagate the error info (monitored task has died)
via poll and read syscalls by returning POLLHUP and 0 respectively.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20140811120102.GY9918@twins.programming.kicks-ass.net
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jean Pihet <jean.pihet@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-t5y3w8jjx6tfo5w8y6oajsjq@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index f0a1036..893a0d0 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -269,6 +269,7 @@
* enum perf_event_active_state - the states of a event
*/
enum perf_event_active_state {
+ PERF_EVENT_STATE_EXIT = -3,
PERF_EVENT_STATE_ERROR = -2,
PERF_EVENT_STATE_OFF = -1,
PERF_EVENT_STATE_INACTIVE = 0,
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 4575dd6..d8cb4d2 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3600,7 +3600,8 @@
* error state (i.e. because it was pinned but it couldn't be
* scheduled on to the CPU at some point).
*/
- if (event->state == PERF_EVENT_STATE_ERROR)
+ if ((event->state == PERF_EVENT_STATE_ERROR) ||
+ (event->state == PERF_EVENT_STATE_EXIT))
return 0;
if (count < event->read_size)
@@ -3630,6 +3631,10 @@
unsigned int events = POLLHUP;
poll_wait(file, &event->waitq, wait);
+
+ if (event->state == PERF_EVENT_STATE_EXIT)
+ return events;
+
/*
* Pin the event->rb by taking event->mmap_mutex; otherwise
* perf_event_set_output() can swizzle our rb and make us miss wakeups.
@@ -7588,6 +7593,9 @@
if (child_event->parent) {
sync_child_event(child_event, child);
free_event(child_event);
+ } else {
+ child_event->state = PERF_EVENT_STATE_EXIT;
+ perf_event_wakeup(child_event);
}
}