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| author | Petr Tesarik <ptesarik@suse.cz> | 2009-05-25 11:02:02 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2009-05-28 14:15:54 +0200 |
| commit | 7d96fd41cadc55f4e00231c8c71b8e25c779f122 (patch) | |
| tree | a52e633f9f7b33f8bd4dead21c22d54f94955293 | |
| parent | cd86a536c81e9300d984327517548ca0652eebf9 (diff) | |
| download | lwn-7d96fd41cadc55f4e00231c8c71b8e25c779f122.tar.gz lwn-7d96fd41cadc55f4e00231c8c71b8e25c779f122.zip | |
x86: move rdtsc_barrier() into the TSC vread method
The *fence instructions were moved to vsyscall_64.c by commit
cb9e35dce94a1b9c59d46224e8a94377d673e204. But this breaks the
vDSO, because vread methods are also called from there.
Besides, the synchronization might be unnecessary for other
time sources than TSC.
[ Impact: fix potential time warp in VDSO ]
Signed-off-by: Petr Tesarik <ptesarik@suse.cz>
LKML-Reference: <9d0ea9ea0f866bdc1f4d76831221ae117f11ea67.1243241859.git.ptesarik@suse.cz>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: <stable@kernel.org>
| -rw-r--r-- | arch/x86/kernel/tsc.c | 11 | ||||
| -rw-r--r-- | arch/x86/kernel/vsyscall_64.c | 8 |
2 files changed, 10 insertions, 9 deletions
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index d57de05dc430..cf8611d991e0 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -710,7 +710,16 @@ static cycle_t read_tsc(struct clocksource *cs) #ifdef CONFIG_X86_64 static cycle_t __vsyscall_fn vread_tsc(void) { - cycle_t ret = (cycle_t)vget_cycles(); + cycle_t ret; + + /* + * Surround the RDTSC by barriers, to make sure it's not + * speculated to outside the seqlock critical section and + * does not cause time warps: + */ + rdtsc_barrier(); + ret = (cycle_t)vget_cycles(); + rdtsc_barrier(); return ret >= __vsyscall_gtod_data.clock.cycle_last ? ret : __vsyscall_gtod_data.clock.cycle_last; diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c index 44153afc9067..25ee06a80aad 100644 --- a/arch/x86/kernel/vsyscall_64.c +++ b/arch/x86/kernel/vsyscall_64.c @@ -132,15 +132,7 @@ static __always_inline void do_vgettimeofday(struct timeval * tv) return; } - /* - * Surround the RDTSC by barriers, to make sure it's not - * speculated to outside the seqlock critical section and - * does not cause time warps: - */ - rdtsc_barrier(); now = vread(); - rdtsc_barrier(); - base = __vsyscall_gtod_data.clock.cycle_last; mask = __vsyscall_gtod_data.clock.mask; mult = __vsyscall_gtod_data.clock.mult; |