linux-kernel - Re: [BUG 2.6.20-rc2-mm1] init segfaults when CONFIG_PROFILE

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Message-Id: <1167594309.14081.79.camel@imap.mvista.com>
Date:	Sun, 31 Dec 2006 11:45:09 -0800
From:	Daniel Walker <dwalker@...sta.com>
To:	Fengguang Wu <fengguang.wu@...il.com>
Cc:	Hua Zhong <hzhong@...il.com>, Andrew Morton <akpm@...l.org>,
	LKML <linux-kernel@...r.kernel.org>, mingo@...e.hu,
	johnstul@...ibm.com
Subject: Re: [BUG 2.6.20-rc2-mm1] init segfaults when
	CONFIG_PROFILE_LIKELY=y

On Sun, 2006-12-31 at 23:04 +0800, Fengguang Wu wrote:
> Hi,
> 
> The following messages keeps popping up when CONFIG_PROFILE_LIKELY=y:
> 
> init[1]: segfault at ffffffff8118c110 rip ffffffff8118c110 rsp 00007fff9a9d14d8 error 15
> init[1]: segfault at ffffffff8118c110 rip ffffffff8118c110 rsp 00007fff9a9d14d8 error 15
> init[1]: segfault at ffffffff8118c110 rip ffffffff8118c110 rsp 00007fff9a9d14d8 error 15
> init[1]: segfault at ffffffff8118c110 rip ffffffff8118c110 rsp 00007fff9a9d14d8 error 15
> init[1]: segfault at ffffffff8118c110 rip ffffffff8118c110 rsp 00007fff9a9d14d8 error 15
> init[1]: segfault at ffffffff8118c110 rip ffffffff8118c110 rsp 00007fff9a9d14d8 error 15
> init[1]: segfault at ffffffff8118c110 rip ffffffff8118c110 rsp 00007fff9a9d14d8 error 15
> init[1]: segfault at ffffffff8118c110 rip ffffffff8118c110 rsp 00007fff9a9d14d8 error 15
> 


Does this seem like an appropriate solution? This just reconstitutes
Ingo's patch by removing the unlikely calls that got added recently. 

Maybe a comment into vsyscall.c that says to stay away from all macro's
and possible debug code that could be added might be helpful ?

Signed-Off-By: Daniel Walker <dwalker@...sta.com>

---
 arch/x86_64/kernel/vsyscall.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

Index: linux-2.6.19/arch/x86_64/kernel/vsyscall.c
===================================================================
--- linux-2.6.19.orig/arch/x86_64/kernel/vsyscall.c
+++ linux-2.6.19/arch/x86_64/kernel/vsyscall.c
@@ -111,7 +111,7 @@ static __always_inline void do_vgettimeo
 		seq = read_seqbegin(&__vsyscall_gtod_data.lock);
 
 		vread = __vsyscall_gtod_data.clock.vread;
-		if (unlikely(!__vsyscall_gtod_data.sysctl_enabled || !vread)) {
+		if (!__vsyscall_gtod_data.sysctl_enabled || !vread) {
 			gettimeofday(tv,0);
 			return;
 		}
@@ -151,7 +151,7 @@ int __vsyscall(0) vgettimeofday(struct t
  * unlikely */
 time_t __vsyscall(1) vtime(time_t *t)
 {
-	if (unlikely(!__vsyscall_gtod_data.sysctl_enabled))
+	if (!__vsyscall_gtod_data.sysctl_enabled)
 		return time_syscall(t);
 	else if (t)
 		*t = __vsyscall_gtod_data.wall_time_tv.tv_sec;


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