35d5d08a08
Marin Mitov points out that delay_tsc() can misbehave if it is preempted and rescheduled on a different CPU which has a skewed TSC. Fix it by disabling preemption. (I assume that the worst-case behaviour here is a stall of 2^32 cycles) Cc: Andi Kleen <ak@suse.de> Cc: Marin Mitov <mitov@issp.bas.bg> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: <stable@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
62 lines
1.2 KiB
C
62 lines
1.2 KiB
C
/*
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* Precise Delay Loops for x86-64
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*
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* Copyright (C) 1993 Linus Torvalds
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* Copyright (C) 1997 Martin Mares <mj@atrey.karlin.mff.cuni.cz>
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*
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* The __delay function must _NOT_ be inlined as its execution time
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* depends wildly on alignment on many x86 processors.
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*/
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#include <linux/module.h>
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#include <linux/sched.h>
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#include <linux/preempt.h>
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#include <linux/delay.h>
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#include <asm/delay.h>
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#include <asm/msr.h>
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#ifdef CONFIG_SMP
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#include <asm/smp.h>
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#endif
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int read_current_timer(unsigned long *timer_value)
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{
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rdtscll(*timer_value);
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return 0;
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}
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void __delay(unsigned long loops)
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{
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unsigned bclock, now;
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preempt_disable(); /* TSC's are pre-cpu */
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rdtscl(bclock);
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do {
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rep_nop();
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rdtscl(now);
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}
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while ((now-bclock) < loops);
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preempt_enable();
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}
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EXPORT_SYMBOL(__delay);
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inline void __const_udelay(unsigned long xloops)
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{
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__delay(((xloops * HZ *
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cpu_data(raw_smp_processor_id()).loops_per_jiffy) >> 32) + 1);
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}
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EXPORT_SYMBOL(__const_udelay);
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void __udelay(unsigned long usecs)
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{
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__const_udelay(usecs * 0x000010c7); /* 2**32 / 1000000 (rounded up) */
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}
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EXPORT_SYMBOL(__udelay);
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void __ndelay(unsigned long nsecs)
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{
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__const_udelay(nsecs * 0x00005); /* 2**32 / 1000000000 (rounded up) */
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}
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EXPORT_SYMBOL(__ndelay);
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