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| author | Andy Lutomirski <luto@MIT.EDU> | 2011-05-23 09:31:31 -0400 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2011-05-24 14:51:29 +0200 |
| commit | 973aa8181e10050809b56ecbaadd01495766a19e (patch) | |
| tree | 0ca3fa4159ab439913a26bba412db5cbbe1737eb /arch/x86/vdso | |
| parent | f144a6b4d1688675d88990e29567b2335b48205e (diff) | |
| download | op-kernel-dev-973aa8181e10050809b56ecbaadd01495766a19e.zip op-kernel-dev-973aa8181e10050809b56ecbaadd01495766a19e.tar.gz | |
x86-64: Optimize vDSO time()
This function just reads a 64-bit variable that's updated
atomically, so we don't need any locks.
Signed-off-by: Andy Lutomirski <luto@mit.edu>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Borislav Petkov <bp@amd64.org>
Link: http://lkml.kernel.org/r/%3C40e2700f8cda4d511e5910be1e633025d28b36c2.1306156808.git.luto%40mit.edu%3E
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'arch/x86/vdso')
| -rw-r--r-- | arch/x86/vdso/vclock_gettime.c | 8 |
1 files changed, 2 insertions, 6 deletions
diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c index e6e9f90..a69929e 100644 --- a/arch/x86/vdso/vclock_gettime.c +++ b/arch/x86/vdso/vclock_gettime.c @@ -180,12 +180,8 @@ notrace time_t __vdso_time(time_t *t) if (unlikely(!VVAR(vsyscall_gtod_data).sysctl_enabled)) return time_syscall(t); - do { - seq = read_seqbegin(&VVAR(vsyscall_gtod_data).lock); - - result = VVAR(vsyscall_gtod_data).wall_time_sec; - - } while (read_seqretry(&VVAR(vsyscall_gtod_data).lock, seq)); + /* This is atomic on x86_64 so we don't need any locks. */ + result = ACCESS_ONCE(VVAR(vsyscall_gtod_data).wall_time_sec); if (t) *t = result; |
