Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752389Ab1DXRFq (ORCPT ); Sun, 24 Apr 2011 13:05:46 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:55337 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750998Ab1DXRFp convert rfc822-to-8bit (ORCPT ); Sun, 24 Apr 2011 13:05:45 -0400 Subject: Re: [PATCH] perf: Allow set output buffer for tasks in the same thread group From: Peter Zijlstra To: Lin Ming Cc: Ingo Molnar , Arnaldo Carvalho de Melo , Tim Blechmann , David Ahern , linux-kernel In-Reply-To: <1303657064.2239.25.camel@localhost> References: <1303657064.2239.25.camel@localhost> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT Date: Sun, 24 Apr 2011 19:05:26 +0200 Message-ID: <1303664726.20212.1.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.30.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 805 Lines: 20 On Sun, 2011-04-24 at 22:57 +0800, Lin Ming wrote: > Currently, kernel only allows an event to redirect its output to other > events of the same task. > > This causes PERF_EVENT_IOC_SET_OUTPUT ioctl fails when an event is > trying to redirect its output to other events in the same thread group. Which is exactly what it should do, you should never be allowed to redirect your events to that of another task, since that other task might be running on another CPU. The buffer code strictly assumes no concurrency, therefore its either one task or one CPU. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/