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. Cc: Adrian Hunter <[email protected]> Cc: Arnaldo Carvalho de Melo <[email protected]> Cc: Corey Ashford <[email protected]> Cc: David Ahern <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Jean Pihet <[email protected]> Cc: Namhyung Kim <[email protected]> Cc: Paul Mackerras <[email protected]> Cc: Peter Zijlstra <[email protected]> Signed-off-by: Jiri Olsa <[email protected]> --- include/linux/perf_event.h | 1 + kernel/events/core.c | 12 ++++++++++-- 2 files changed, 11 insertions(+), 2 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 707617a8c0f6..54f3a6241386 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -268,6 +268,7 @@ struct pmu { * 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 14086e45c5c4..dde0eefa410a 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3499,7 +3499,8 @@ perf_read_hw(struct perf_event *event, char __user *buf, size_t count) * 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) @@ -3526,9 +3527,13 @@ static unsigned int perf_poll(struct file *file, poll_table *wait) { struct perf_event *event = file->private_data; struct ring_buffer *rb; - unsigned int events = POLL_HUP; + unsigned int events = POLLHUP; poll_wait(file, &event->waitq, wait); + + if (event->state == PERF_EVENT_STATE_EXIT) + return POLLHUP; + /* * Pin the event->rb by taking event->mmap_mutex; otherwise * perf_event_set_output() can swizzle our rb and make us miss wakeups. @@ -7484,6 +7489,9 @@ __perf_event_exit_task(struct perf_event *child_event, 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); } } -- 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/
