Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757087AbZKSPnz (ORCPT ); Thu, 19 Nov 2009 10:43:55 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756859AbZKSPny (ORCPT ); Thu, 19 Nov 2009 10:43:54 -0500 Received: from ey-out-2122.google.com ([74.125.78.25]:49955 "EHLO ey-out-2122.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755865AbZKSPnx (ORCPT ); Thu, 19 Nov 2009 10:43:53 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:cc:subject:message-id:references:mime-version :content-type:content-disposition:in-reply-to:user-agent; b=i/K6twJpGFDvW3I6hhshfIdyMEebdiVt2koETaG6wfz9Py2oetfixnHjB8gSZ9u1Qa EMAVQBUqXc/9cGeCBMbYroxfKbaDqkCj5dY5UdtmZ/IBxKJRrIQpGD77ZfQCcmLm8hVm PeAccDe3dvSCmNTQ+qchcLXyW6UCh6LnYxoVI= Date: Thu, 19 Nov 2009 16:43:56 +0100 From: Frederic Weisbecker To: Peter Zijlstra Cc: Ingo Molnar , LKML , Li Zefan , Prasad , Alan Stern , Arnaldo Carvalho de Melo , Steven Rostedt , Jan Kiszka , Jiri Slaby , Avi Kivity , Paul Mackerras , Mike Galbraith , Masami Hiramatsu , Paul Mundt , Arjan van de Ven Subject: Re: [PATCH 3/7 v6] perf/core: Add a callback to perf events Message-ID: <20091119154349.GA4967@nowhere> References: <1257694141-5670-1-git-send-email-fweisbec@gmail.com> <1257694141-5670-4-git-send-email-fweisbec@gmail.com> <1258457333.7816.186.camel@laptop> <20091118001815.GA8187@nowhere> <1258536669.3918.99.camel@laptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1258536669.3918.99.camel@laptop> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1745 Lines: 44 On Wed, Nov 18, 2009 at 10:31:09AM +0100, Peter Zijlstra wrote: > On Wed, 2009-11-18 at 01:18 +0100, Frederic Weisbecker wrote: > > On Tue, Nov 17, 2009 at 12:28:53PM +0100, Peter Zijlstra wrote: > > > On Sun, 2009-11-08 at 16:28 +0100, Frederic Weisbecker wrote: > > > > A simple callback in a perf event can be used for multiple purposes. > > > > For example it is useful for triggered based events like hardware > > > > breakpoints that need a callback to dispatch a triggered breakpoint > > > > event. > > > > > > > > v2: Simplify a bit the callback attribution as suggested by Paul > > > > Mackerras > > > > > > Yuck! So we add an opaque callback without semantics nor usage. > > > > > > Yeah, this is intended for events that need to be able to trigger > > events to different channels. In the case of hw-breakpoints, it's > > either perf buffer, ptrace, etc... > > > > Should I add some comments about it? > > At the very least.. describe its semantics and preferably rename the > thing. May be "event_triggered"? > Currently I've no clue what it does and why, your description above > about multiple channels does not at all help me understand how this > function pointer is used to make that happen. > We need it for hardware breakpoints because if we register a breakpoint for perf syscall use, we need to dispatch the event to perf. But if we register it for ptrace, or any in-kernel uses, we need to dispatch the event somewhere else and then we need another callback. -- 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/