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author | Ingo Molnar <mingo@elte.hu> | 2008-11-08 19:27:00 (GMT) |
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committer | Ingo Molnar <mingo@elte.hu> | 2008-11-08 19:27:00 (GMT) |
commit | cb9e35dce94a1b9c59d46224e8a94377d673e204 (patch) | |
tree | e3772e7d6ed11d1c1c648799e78619f782e5e090 | |
parent | 895e031707954a9ca26ed4f5f794575313854ed1 (diff) | |
download | linux-fsl-qoriq-cb9e35dce94a1b9c59d46224e8a94377d673e204.tar.xz |
x86: clean up rdtsc_barrier() use
Impact: cleanup
Move rdtsc_barrier() use to vsyscall_64.c where it's relied on,
and point out its role in the context of its use.
Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r-- | arch/x86/include/asm/tsc.h | 6 | ||||
-rw-r--r-- | arch/x86/kernel/vsyscall_64.c | 9 |
2 files changed, 10 insertions, 5 deletions
diff --git a/arch/x86/include/asm/tsc.h b/arch/x86/include/asm/tsc.h index 9cd83a8..700aeb8 100644 --- a/arch/x86/include/asm/tsc.h +++ b/arch/x86/include/asm/tsc.h @@ -44,11 +44,7 @@ static __always_inline cycles_t vget_cycles(void) if (!cpu_has_tsc) return 0; #endif - rdtsc_barrier(); - cycles = (cycles_t)__native_read_tsc(); - rdtsc_barrier(); - - return cycles; + return (cycles_t)__native_read_tsc(); } extern void tsc_init(void); diff --git a/arch/x86/kernel/vsyscall_64.c b/arch/x86/kernel/vsyscall_64.c index 0b8b6690..ebf2f12 100644 --- a/arch/x86/kernel/vsyscall_64.c +++ b/arch/x86/kernel/vsyscall_64.c @@ -128,7 +128,16 @@ static __always_inline void do_vgettimeofday(struct timeval * tv) gettimeofday(tv,NULL); 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; |