2.6.23-stable review patch. If anyone has any objections, please let us know. ------------------ From: Andrew Morton patch 35d5d08a085c56f153458c3f5d8ce24123617faf in mainline. 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 Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- arch/i386/lib/delay.c | 3 +++ arch/x86_64/lib/delay.c | 11 +++++++---- 2 files changed, 10 insertions(+), 4 deletions(-) --- a/arch/i386/lib/delay.c +++ b/arch/i386/lib/delay.c @@ -12,6 +12,7 @@ #include #include +#include #include #include @@ -42,11 +43,13 @@ static void delay_tsc(unsigned long loop { unsigned long bclock, now; + preempt_disable(); /* TSC's are per-cpu */ rdtscl(bclock); do { rep_nop(); rdtscl(now); } while ((now-bclock) < loops); + preempt_enable(); } /* --- a/arch/x86_64/lib/delay.c +++ b/arch/x86_64/lib/delay.c @@ -10,7 +10,9 @@ #include #include +#include #include + #include #include @@ -27,14 +29,15 @@ int read_current_timer(unsigned long *ti 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); -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/