From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754485AbaIVQzN (ORCPT ); Mon, 22 Sep 2014 12:55:13 -0400 Received: from mail-ig0-f176.google.com ([209.85.213.176]:44280 "EHLO mail-ig0-f176.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753958AbaIVQzL (ORCPT ); Mon, 22 Sep 2014 12:55:11 -0400 Message-ID: <5420546D.6050102@gmail.com> Date: Mon, 22 Sep 2014 09:55:09 -0700 From: David Daney User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 MIME-Version: 1.0 To: Markos Chandras CC: linux-mips@linux-mips.org, Steven Rostedt , Ingo Molnar , linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] MIPS: ftrace.h: Fix the MCOUNT_INSN_SIZE definition References: <1411392779-9554-1-git-send-email-markos.chandras@imgtec.com> <1411392779-9554-2-git-send-email-markos.chandras@imgtec.com> In-Reply-To: <1411392779-9554-2-git-send-email-markos.chandras@imgtec.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/22/2014 06:32 AM, Markos Chandras wrote: > The MCOUNT_INSN_SIZE is meant to be used to denote the overall > size of the mcount() call. Since a jal instruction is used to > call mcount() the delay slot should be taken into consideration > as well. > This also replaces the MCOUNT_INSN_SIZE usage with the real size > of a single MIPS instruction since, as described above, the > MCOUNT_INSN_SIZE is used to denote the total overhead of the > mcount() call. Are you seeing errors with the existing code? If so please state what they are. By changing this, we can no longer atomically replace the instruction. So I think shouldn't be changing this stuff unless there is a real bug we are fixing. In conclusion: NAK unless the patch fixes a bug, in which case the change log *must* state what the bug is, and how the patch addresses the problem. David Daney > > Cc: Steven Rostedt > Cc: Ingo Molnar > Cc: linux-kernel@vger.kernel.org > Signed-off-by: Markos Chandras > --- > arch/mips/include/asm/ftrace.h | 2 +- > arch/mips/kernel/ftrace.c | 4 +++- > 2 files changed, 4 insertions(+), 2 deletions(-) > > diff --git a/arch/mips/include/asm/ftrace.h b/arch/mips/include/asm/ftrace.h > index 992aaba603b5..70d4a35fb560 100644 > --- a/arch/mips/include/asm/ftrace.h > +++ b/arch/mips/include/asm/ftrace.h > @@ -13,7 +13,7 @@ > #ifdef CONFIG_FUNCTION_TRACER > > #define MCOUNT_ADDR ((unsigned long)(_mcount)) > -#define MCOUNT_INSN_SIZE 4 /* sizeof mcount call */ > +#define MCOUNT_INSN_SIZE 8 /* sizeof mcount call + delay slot */ > > #ifndef __ASSEMBLY__ > extern void _mcount(void); > diff --git a/arch/mips/kernel/ftrace.c b/arch/mips/kernel/ftrace.c > index 937c54bc8ccc..211460d4617d 100644 > --- a/arch/mips/kernel/ftrace.c > +++ b/arch/mips/kernel/ftrace.c > @@ -28,6 +28,8 @@ > #define MCOUNT_OFFSET_INSNS 4 > #endif > > +#define FTRACE_MIPS_INSN_SIZE 4 /* Size of single MIPS instruction */ > + > #ifdef CONFIG_DYNAMIC_FTRACE > > /* Arch override because MIPS doesn't need to run this from stop_machine() */ > @@ -395,7 +397,7 @@ void prepare_ftrace_return(unsigned long *parent_ra_addr, unsigned long self_ra, > */ > > insns = in_kernel_space(self_ra) ? 2 : MCOUNT_OFFSET_INSNS + 1; > - trace.func = self_ra - (MCOUNT_INSN_SIZE * insns); > + trace.func = self_ra - (FTRACE_MIPS_INSN_SIZE * insns); > > /* Only trace if the calling function expects to */ > if (!ftrace_graph_entry(&trace)) { >