From 35d5d08a085c56f153458c3f5d8ce24123617faf Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Wed, 14 Nov 2007 17:00:41 -0800 Subject: [PATCH] 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 Cc: Marin Mitov Cc: Thomas Gleixner Cc: Ingo Molnar Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/x86/lib/delay_32.c | 3 +++ arch/x86/lib/delay_64.c | 11 +++++++---- 2 files changed, 10 insertions(+), 4 deletions(-) diff --git a/arch/x86/lib/delay_32.c b/arch/x86/lib/delay_32.c index 952e7a89c2ac..aad9d95469dc 100644 --- a/arch/x86/lib/delay_32.c +++ b/arch/x86/lib/delay_32.c @@ -12,6 +12,7 @@ #include #include +#include #include #include @@ -42,11 +43,13 @@ static void delay_tsc(unsigned long loops) { unsigned long bclock, now; + preempt_disable(); /* TSC's are per-cpu */ rdtscl(bclock); do { rep_nop(); rdtscl(now); } while ((now-bclock) < loops); + preempt_enable(); } /* diff --git a/arch/x86/lib/delay_64.c b/arch/x86/lib/delay_64.c index 0ebbfb9e7c7f..45cdd3fbd91c 100644 --- a/arch/x86/lib/delay_64.c +++ b/arch/x86/lib/delay_64.c @@ -10,7 +10,9 @@ #include #include +#include #include + #include #include @@ -27,14 +29,15 @@ int read_current_timer(unsigned long *timer_value) void __delay(unsigned long loops) { unsigned bclock, now; - + + preempt_disable(); /* TSC's are pre-cpu */ rdtscl(bclock); - do - { + do { rep_nop(); rdtscl(now); } - while((now-bclock) < loops); + while ((now-bclock) < loops); + preempt_enable(); } EXPORT_SYMBOL(__delay); -- 2.20.1