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Groups > linux.kernel > #1664765 > unrolled thread

[RFC PATCH v2 1/2] kernel/events: Add option to notify through signals on wakeup

Started by"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
First post2017-06-13 13:40 +0200
Last post2017-06-13 17:20 +0200
Articles 3 — 2 participants

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  [RFC PATCH v2 1/2] kernel/events: Add option to notify through signals on wakeup "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2017-06-13 13:40 +0200
    Re: [RFC PATCH v2 1/2] kernel/events: Add option to notify through  signals on wakeup Jiri Olsa <jolsa@redhat.com> - 2017-06-13 16:50 +0200
      Re: [RFC PATCH v2 1/2] kernel/events: Add option to notify through  signals on wakeup "Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com> - 2017-06-13 17:20 +0200

#1664765 — [RFC PATCH v2 1/2] kernel/events: Add option to notify through signals on wakeup

From"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Date2017-06-13 13:40 +0200
Subject[RFC PATCH v2 1/2] kernel/events: Add option to notify through signals on wakeup
Message-ID<tRSkV-7nC-1@gated-at.bofh.it>
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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#1664934 — Re: [RFC PATCH v2 1/2] kernel/events: Add option to notify through signals on wakeup

FromJiri Olsa <jolsa@redhat.com>
Date2017-06-13 16:50 +0200
SubjectRe: [RFC PATCH v2 1/2] kernel/events: Add option to notify through signals on wakeup
Message-ID<tRViN-Jw-7@gated-at.bofh.it>
In reply to#1664765
On Tue, Jun 13, 2017 at 05:03:42PM +0530, Naveen N. Rao wrote:

SNIP

> 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;
> +

since it's signal_on_wakeup, should we also send POLL_HUP for
perf_event_wakeup calls from perf_event_exit_event?

jirka

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#1664956 — Re: [RFC PATCH v2 1/2] kernel/events: Add option to notify through signals on wakeup

From"Naveen N. Rao" <naveen.n.rao@linux.vnet.ibm.com>
Date2017-06-13 17:20 +0200
SubjectRe: [RFC PATCH v2 1/2] kernel/events: Add option to notify through signals on wakeup
Message-ID<tRVLP-19S-9@gated-at.bofh.it>
In reply to#1664934
Hi Jiri,

On 2017/06/13 04:45PM, Jiri Olsa wrote:
> On Tue, Jun 13, 2017 at 05:03:42PM +0530, Naveen N. Rao wrote:
> 
> SNIP
> 
> > 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;
> > +
> 
> since it's signal_on_wakeup, should we also send POLL_HUP for
> perf_event_wakeup calls from perf_event_exit_event?

Yes, I suspect so (though I'm open to changing the name ;)
I haven't handled POLL_HUP properly in this patch, including 
IOC_REFRESH. I will look into that next.

I wanted to know if the overall approach is fine -- between RFC v1 vs.  
this version.

Thanks for the review!
- Naveen

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