linux-kernel - Re: [PATCH -v6 05/13] tracing: enable HAVE_FUNCTION_TRACE_MCOUNT

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Date:	Mon, 26 Oct 2009 11:57:20 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Sergei Shtylyov <sshtylyov@...mvista.com>
Cc:	Wu Zhangjin <wuzhangjin@...il.com>, linux-mips@...ux-mips.org,
	linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Richard Sandiford <rdsandiford@...glemail.com>,
	Nicholas Mc Guire <der.herr@...r.at>,
	David Daney <ddaney@...iumnetworks.com>,
	Adam Nemet <anemet@...iumnetworks.com>,
	Patrik Kluba <kpajko79@...il.com>
Subject: Re: [PATCH -v6 05/13] tracing: enable
 HAVE_FUNCTION_TRACE_MCOUNT_TEST for MIPS

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@...il.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@...ote.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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