95492e4646
make the TSC synchronization code more robust, and unify it between x86_64 and i386. The biggest change is the removal of the 'fix up TSCs' code on x86_64 and i386, in some rare cases it was /causing/ time-warps on SMP systems. The new code only checks for TSC asynchronity - and if it can prove a time-warp (if it can observe the TSC going backwards when going from one CPU to another within a critical section), then the TSC clock-source is turned off. The TSC synchronization-checking code also got moved into a separate file. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Cc: john stultz <johnstul@us.ibm.com> Cc: Roman Zippel <zippel@linux-m68k.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
67 lines
1.2 KiB
C
67 lines
1.2 KiB
C
/*
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* linux/include/asm-x86_64/tsc.h
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*
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* x86_64 TSC related functions
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*/
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#ifndef _ASM_x86_64_TSC_H
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#define _ASM_x86_64_TSC_H
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#include <asm/processor.h>
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/*
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* Standard way to access the cycle counter.
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*/
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typedef unsigned long long cycles_t;
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extern unsigned int cpu_khz;
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extern unsigned int tsc_khz;
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static inline cycles_t get_cycles(void)
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{
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unsigned long long ret = 0;
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#ifndef CONFIG_X86_TSC
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if (!cpu_has_tsc)
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return 0;
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#endif
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#if defined(CONFIG_X86_GENERIC) || defined(CONFIG_X86_TSC)
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rdtscll(ret);
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#endif
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return ret;
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}
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/* Like get_cycles, but make sure the CPU is synchronized. */
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static __always_inline cycles_t get_cycles_sync(void)
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{
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unsigned long long ret;
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#ifdef X86_FEATURE_SYNC_RDTSC
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unsigned eax;
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/*
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* Don't do an additional sync on CPUs where we know
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* RDTSC is already synchronous:
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*/
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alternative_io("cpuid", ASM_NOP2, X86_FEATURE_SYNC_RDTSC,
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"=a" (eax), "0" (1) : "ebx","ecx","edx","memory");
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#else
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sync_core();
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#endif
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rdtscll(ret);
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return ret;
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}
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extern void tsc_init(void);
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extern void mark_tsc_unstable(void);
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extern int unsynchronized_tsc(void);
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/*
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* Boot-time check whether the TSCs are synchronized across
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* all CPUs/cores:
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*/
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extern void check_tsc_sync_source(int cpu);
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extern void check_tsc_sync_target(void);
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#endif
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