From: Eric Dumazet <dada1@cosmosbay.com>
Date: Wed, 2 May 2007 17:27:11 +0000 (+0200)
Subject: [PATCH] x86-64: fix vtime() vsyscall
X-Git-Tag: v2.6.22-rc1~1011^2~133
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=272a3713bb9e302e0455c894c41180a482d2c8a3;p=linux-2.6-omap-h63xx.git

[PATCH] x86-64: fix vtime() vsyscall

There is a tiny probability that the return value from vtime(time_t *t) is
Signed-off-by: Andi Kleen <ak@suse.de>

different than the value stored in *t

Using a temporary variable solves the problem and gives a faster code.

   17:   48 85 ff                test   %rdi,%rdi
   1a:   48 8b 05 00 00 00 00    mov    0(%rip),%rax        #
__vsyscall_gtod_data.wall_time_tv.tv_sec
   21:   74 03                   je     26
   23:   48 89 07                mov    %rax,(%rdi)
   26:   c9                      leaveq
   27:   c3                      retq

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
---

diff --git a/arch/x86_64/kernel/vsyscall.c b/arch/x86_64/kernel/vsyscall.c
index d14cbb3e0eb..ba330f87067 100644
--- a/arch/x86_64/kernel/vsyscall.c
+++ b/arch/x86_64/kernel/vsyscall.c
@@ -156,11 +156,13 @@ int __vsyscall(0) vgettimeofday(struct timeval * tv, struct timezone * tz)
  * unlikely */
 time_t __vsyscall(1) vtime(time_t *t)
 {
+	time_t result;
 	if (unlikely(!__vsyscall_gtod_data.sysctl_enabled))
 		return time_syscall(t);
-	else if (t)
-		*t = __vsyscall_gtod_data.wall_time_tv.tv_sec;
-	return __vsyscall_gtod_data.wall_time_tv.tv_sec;
+	result = __vsyscall_gtod_data.wall_time_tv.tv_sec;
+	if (t)
+		*t = result;
+	return result;
 }
 
 /* Fast way to get current CPU and node.