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Re: [PATCH -v6 05/13] tracing: enable HAVE_FUNCTION_TRACE_MCOUNT_TEST fo

To: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Subject: Re: [PATCH -v6 05/13] tracing: enable HAVE_FUNCTION_TRACE_MCOUNT_TEST for MIPS
From: Steven Rostedt <rostedt@goodmis.org>
Date: Mon, 26 Oct 2009 11:57:20 -0400
Cc: Wu Zhangjin <wuzhangjin@gmail.com>, linux-mips@linux-mips.org, linux-kernel@vger.kernel.org, Frederic Weisbecker <fweisbec@gmail.com>, Thomas Gleixner <tglx@linutronix.de>, Ralf Baechle <ralf@linux-mips.org>, Richard Sandiford <rdsandiford@googlemail.com>, Nicholas Mc Guire <der.herr@hofr.at>, David Daney <ddaney@caviumnetworks.com>, Adam Nemet <anemet@caviumnetworks.com>, Patrik Kluba <kpajko79@gmail.com>
In-reply-to: <4AE5C344.4020104@ru.mvista.com>
Organization: Kihon Technologies Inc.
Original-recipient: rfc822;linux-mips@linux-mips.org
References: <cover.1256569489.git.wuzhangjin@gmail.com> <747deea2f18d5ccffe842df95a9dd1c86251a958.1256569489.git.wuzhangjin@gmail.com> <3f47087b70a965fd679b17a59521671296457df1.1256569489.git.wuzhangjin@gmail.com> <f290e125634d164ec65b09b24b269815f78455ab.1256569489.git.wuzhangjin@gmail.com> <07dc907ec62353b1aca99b2850d3b2e4b734189a.1256569489.git.wuzhangjin@gmail.com> <374da7039d2e1b97083edd8bcd7811356884d427.1256569489.git.wuzhangjin@gmail.com> <4AE5C344.4020104@ru.mvista.com>
Reply-to: rostedt@goodmis.org
Sender: linux-mips-bounce@linux-mips.org
On Mon, 2009-10-26 at 18:41 +0300, Sergei Shtylyov wrote:
> Hello.
> 
> Wu Zhangjin wrote:
> 
> > There is an exisiting common ftrace_test_stop_func() in
> > kernel/trace/ftrace.c, which is used to check the global variable
> > ftrace_trace_stop to determine whether stop the function tracing.
> 
> > This patch implepment the MIPS specific one to speedup the procedure.
> 
> > Thanks goes to Zhang Le for Cleaning it up.
> 
> > Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
> 
> [...]
> 
> > diff --git a/arch/mips/kernel/mcount.S b/arch/mips/kernel/mcount.S
> > index 0c39bc8..5dfaca8 100644
> > --- a/arch/mips/kernel/mcount.S
> > +++ b/arch/mips/kernel/mcount.S
> > @@ -64,6 +64,10 @@
> >     .endm
> >  
> >  NESTED(_mcount, PT_SIZE, ra)
> > +   lw      t0, function_trace_stop
> > +   bnez    t0, ftrace_stub
> > +   nop
> 
> 1) unless .set noreorder is specified in this file, explicit nop is not 
> needed;

>From patch 4:

+++ b/arch/mips/kernel/mcount.S
@@ -0,0 +1,89 @@
+/*
+ * MIPS specific _mcount support
+ *
+ * This file is subject to the terms and conditions of the GNU General
Public
+ * License.  See the file "COPYING" in the main directory of this
archive for
+ * more details.
+ *
+ * Copyright (C) 2009 Lemote Inc. & DSLab, Lanzhou University, China
+ * Author: Wu Zhangjin <wuzj@lemote.com>
+ */
+
+#include <asm/regdef.h>
+#include <asm/stackframe.h>
+#include <asm/ftrace.h>
+
+       .text
+       .set noreorder
+       .set noat

-- Steve

> 
> 2) delay slot instruction is usually denoted by adding extra space on its 
> left, like this:
> 
>       bnez    t0, ftrace_stub
>        nop





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