forked from luck/tmp_suning_uos_patched
x86: disable preemption in delay_tsc()
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>
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@ -12,6 +12,7 @@
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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/processor.h>
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@ -42,11 +43,13 @@ static void delay_tsc(unsigned long loops)
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{
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unsigned long bclock, now;
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preempt_disable(); /* TSC's are per-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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} while ((now-bclock) < loops);
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preempt_enable();
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}
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/*
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@ -10,7 +10,9 @@
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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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@ -27,14 +29,15 @@ int read_current_timer(unsigned long *timer_value)
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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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{
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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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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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