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Subject[RFC PATCH v2 1/2] kernel/events: Add option to notify through signals on wakeup
Date
Add a new option 'signal_on_wakeup' to request for a signal to be
delivered on ring buffer wakeup controlled through watermark and
{wakeup_events, wakeup_watermark}.

Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
---
include/uapi/linux/perf_event.h | 3 ++-
kernel/events/core.c | 12 +++++++-----
kernel/events/ring_buffer.c | 3 +++
3 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h
index b1c0b187acfe..e5810b1d74a4 100644
--- a/include/uapi/linux/perf_event.h
+++ b/include/uapi/linux/perf_event.h
@@ -345,7 +345,8 @@ struct perf_event_attr {
context_switch : 1, /* context switch data */
write_backward : 1, /* Write ring buffer from end to beginning */
namespaces : 1, /* include namespaces data */
- __reserved_1 : 35;
+ signal_on_wakeup : 1, /* send signal on wakeup */
+ __reserved_1 : 34;

union {
__u32 wakeup_events; /* wakeup every n events */
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6c4e523dc1e2..73ad30e124e5 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7362,12 +7362,14 @@ static int __perf_event_overflow(struct perf_event *event,
* events
*/

- event->pending_kill = POLL_IN;
- if (events && atomic_dec_and_test(&event->event_limit)) {
- ret = 1;
- event->pending_kill = POLL_HUP;
+ if (!event->attr.signal_on_wakeup) {
+ event->pending_kill = POLL_IN;
+ if (events && atomic_dec_and_test(&event->event_limit)) {
+ ret = 1;
+ event->pending_kill = POLL_HUP;

- perf_event_disable_inatomic(event);
+ perf_event_disable_inatomic(event);
+ }
}

READ_ONCE(event->overflow_handler)(event, data, regs);
diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c
index 2831480c63a2..4e7c728569a8 100644
--- a/kernel/events/ring_buffer.c
+++ b/kernel/events/ring_buffer.c
@@ -21,6 +21,9 @@ static void perf_output_wakeup(struct perf_output_handle *handle)
{
atomic_set(&handle->rb->poll, POLLIN);

+ if (handle->event->attr.signal_on_wakeup)
+ handle->event->pending_kill = POLL_IN;
+
handle->event->pending_wakeup = 1;
irq_work_queue(&handle->event->pending);
}
--
2.12.2
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