87 lines
2.0 KiB
C
87 lines
2.0 KiB
C
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#include <linux/sched.h>
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#include <linux/init.h>
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#include <linux/module.h>
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#include <linux/timer.h>
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unsigned int cpu_khz; /* TSC clocks / usec, not used here */
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EXPORT_SYMBOL(cpu_khz);
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unsigned int tsc_khz;
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EXPORT_SYMBOL(tsc_khz);
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/*
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* TSC can be unstable due to cpufreq or due to unsynced TSCs
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*/
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int tsc_unstable;
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/* native_sched_clock() is called before tsc_init(), so
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we must start with the TSC soft disabled to prevent
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erroneous rdtsc usage on !cpu_has_tsc processors */
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int tsc_disabled = -1;
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/*
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* Scheduler clock - returns current time in nanosec units.
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*/
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u64 native_sched_clock(void)
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{
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u64 this_offset;
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/*
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* Fall back to jiffies if there's no TSC available:
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* ( But note that we still use it if the TSC is marked
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* unstable. We do this because unlike Time Of Day,
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* the scheduler clock tolerates small errors and it's
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* very important for it to be as fast as the platform
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* can achive it. )
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*/
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if (unlikely(tsc_disabled)) {
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/* No locking but a rare wrong value is not a big deal: */
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return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ);
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}
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/* read the Time Stamp Counter: */
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rdtscll(this_offset);
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/* return the value in ns */
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return cycles_2_ns(this_offset);
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}
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/* We need to define a real function for sched_clock, to override the
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weak default version */
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#ifdef CONFIG_PARAVIRT
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unsigned long long sched_clock(void)
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{
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return paravirt_sched_clock();
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}
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#else
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unsigned long long
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sched_clock(void) __attribute__((alias("native_sched_clock")));
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#endif
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int check_tsc_unstable(void)
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{
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return tsc_unstable;
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}
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EXPORT_SYMBOL_GPL(check_tsc_unstable);
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#ifdef CONFIG_X86_TSC
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int __init notsc_setup(char *str)
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{
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printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, "
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"cannot disable TSC completely.\n");
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tsc_disabled = 1;
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return 1;
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}
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#else
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/*
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* disable flag for tsc. Takes effect by clearing the TSC cpu flag
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* in cpu/common.c
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*/
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int __init notsc_setup(char *str)
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{
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setup_clear_cpu_cap(X86_FEATURE_TSC);
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return 1;
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}
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#endif
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__setup("notsc", notsc_setup);
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