From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754595AbbE1TAy (ORCPT ); Thu, 28 May 2015 15:00:54 -0400 Received: from mail-qg0-f51.google.com ([209.85.192.51]:35501 "EHLO mail-qg0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752130AbbE1TAp (ORCPT ); Thu, 28 May 2015 15:00:45 -0400 From: Vince Weaver X-Google-Original-From: Vince Weaver Date: Thu, 28 May 2015 15:06:19 -0400 (EDT) To: linux-kernel@vger.kernel.org cc: mingo@kernel.org, peterz@infradead.org, eranian@google.com, Paul Mackerras , Arnaldo Carvalho de Melo Subject: [patch] inherited events not signalling parent on overflow Message-ID: User-Agent: Alpine 2.11 (DEB 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org We're trying to get self-monitoring multi-threaded sampling working in PAPI. Fun times. Is this even possible? Ideally in your parent thread you could perf_event_open() with inherit set. Then your program (say an OpenMP program) would do its thing and all of the samples would get written back to the parent thread's mmap() buffer. But this won't work as mmap'ing an inherited event is explicitly disasllowed in events.c due to "performance reasons". Which is believable, it's just there's not really a good alternative that doesn't involve having to somehow manually instrument every single possible thread. on a related note, I turned up the following issue when working on this issue. I don't know if this is the proper fix but it makes my simple test case behave as expected. If we inherit events, we inherit the signal state but not the fasync state, so overflows in inherited children will never trigger the signal handler. Signed-off-by: Vince Weaver diff --git a/kernel/events/core.c b/kernel/events/core.c index 1a3bf48..7df4cf5 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -8626,6 +8630,8 @@ inherit_event(struct perf_event *parent_event, child_event->overflow_handler_context = parent_event->overflow_handler_context; + child_event->fasync = parent_event->fasync; + /* * Precalculate sample_data sizes */