From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f50.google.com (mail-pa0-f50.google.com [209.85.220.50]) by kanga.kvack.org (Postfix) with ESMTP id 521C76B0253 for ; Thu, 3 Dec 2015 17:10:13 -0500 (EST) Received: by pacdm15 with SMTP id dm15so75562072pac.3 for ; Thu, 03 Dec 2015 14:10:13 -0800 (PST) Received: from mail-pa0-x22f.google.com (mail-pa0-x22f.google.com. [2607:f8b0:400e:c03::22f]) by mx.google.com with ESMTPS id u84si14461713pfi.160.2015.12.03.14.10.12 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 03 Dec 2015 14:10:12 -0800 (PST) Received: by pabfh17 with SMTP id fh17so77848396pab.0 for ; Thu, 03 Dec 2015 14:10:12 -0800 (PST) Message-ID: <5660BDC2.5060400@linaro.org> Date: Thu, 03 Dec 2015 14:10:10 -0800 From: "Shi, Yang" MIME-Version: 1.0 Subject: Re: [PATCH V2 2/7] mm/gup: add gup trace points References: <1449096813-22436-1-git-send-email-yang.shi@linaro.org> <1449096813-22436-3-git-send-email-yang.shi@linaro.org> <565F8092.7000001@intel.com> <20151202231348.7058d6e2@grimm.local.home> <56608BA2.2050300@linaro.org> <20151203140614.75f49aad@gandalf.local.home> In-Reply-To: <20151203140614.75f49aad@gandalf.local.home> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Steven Rostedt Cc: Dave Hansen , akpm@linux-foundation.org, mingo@redhat.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linaro-kernel@lists.linaro.org On 12/3/2015 11:06 AM, Steven Rostedt wrote: > On Thu, 03 Dec 2015 10:36:18 -0800 > "Shi, Yang" wrote: > >>> called directly that calls these functions internally and the tracepoint >>> can trap the return value. >> >> This will incur more changes in other subsystems (futex, kvm, etc), I'm >> not sure if it is worth making such changes to get return value. > > No, it wouldn't require any changes outside of this. > > -long __get_user_pages(..) > +static long __get_user_pages_internal(..) > { > [..] > } > + > +long __get_user_pages(..) > +{ > + long ret; > + ret = __get_user_pages_internal(..); > + trace_get_user_pages(.., ret) > +} Thanks for this. I just checked the fast version, it looks it just has single return path, so this should be just needed by slow version. > >> >>> I can probably make function_graph tracer give return values, although >>> it will give a return value for void functions as well. And it may give >>> long long returns for int returns that may have bogus data in the >>> higher bits. >> >> If the return value requirement is not limited to gup, the approach >> sounds more reasonable. >> > > Others have asked about it. Maybe I should do it. If you are going to add return value in common trace code, I won't do the gup specific one in V3. Thanks, Yang > > -- Steve > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org