Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756766AbdGLLqd (ORCPT ); Wed, 12 Jul 2017 07:46:33 -0400 Received: from bombadil.infradead.org ([65.50.211.133]:37573 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756510AbdGLLqb (ORCPT ); Wed, 12 Jul 2017 07:46:31 -0400 Date: Wed, 12 Jul 2017 13:46:27 +0200 From: Peter Zijlstra To: "Naveen N. Rao" Cc: Arnaldo Carvalho de Melo , Jiri Olsa , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] kernel/events: Add option to notify through signals on wakeup Message-ID: <20170712114627.hm4pj6kybxgdre3b@hirez.programming.kicks-ass.net> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2176 Lines: 71 On Mon, Jun 19, 2017 at 08:01:07PM +0530, Naveen N. Rao wrote: > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 6c4e523dc1e2..812fcfc767f4 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -2679,7 +2679,8 @@ static int _perf_event_refresh(struct perf_event *event, int refresh) > /* > * not supported on inherited events That comment wants updating to explain the signal crud.. > */ > - if (event->attr.inherit || !is_sampling_event(event)) > + if (event->attr.inherit || event->attr.signal_on_wakeup || > + !is_sampling_event(event)) > return -EINVAL; > > atomic_add(refresh, &event->event_limit); > @@ -7362,12 +7362,15 @@ static int __perf_event_overflow(struct perf_event *event, > * events > */ > > + if (!event->attr.signal_on_wakeup) { > + int events = atomic_read(&event->event_limit); > + 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); > + } > } So even without event_limit (IOC_REFRESH) this would've generated SIGIO:POLL_IN. > > READ_ONCE(event->overflow_handler)(event, data, regs); > @@ -10408,6 +10411,7 @@ perf_event_exit_event(struct perf_event *child_event, > perf_group_detach(child_event); > list_del_event(child_event, child_ctx); > child_event->state = PERF_EVENT_STATE_EXIT; /* is_event_hup() */ > + child_event->pending_kill = POLL_HUP; This looks like an undocumented change.. > raw_spin_unlock_irq(&child_ctx->lock); > > /* > 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; > + And this is the bit that generates SIGIO:POLL_IN on wakeup. > handle->event->pending_wakeup = 1; > irq_work_queue(&handle->event->pending); > } > -- > 2.13.1 >