diff options
| author | Andrew Morton <akpm@linux-foundation.org> | 2007-11-15 02:00:41 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-11-15 03:45:44 +0100 |
| commit | 35d5d08a085c56f153458c3f5d8ce24123617faf (patch) | |
| tree | 2db6e598e87809bc1ce7838861b2cff18e5fe60d /arch/x86/lib | |
| parent | keyspan: init termios properly (diff) | |
| download | linux-35d5d08a085c56f153458c3f5d8ce24123617faf.tar.xz linux-35d5d08a085c56f153458c3f5d8ce24123617faf.zip | |
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>
Diffstat (limited to 'arch/x86/lib')
| -rw-r--r-- | arch/x86/lib/delay_32.c | 3 | ||||
| -rw-r--r-- | 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 <linux/module.h> #include <linux/sched.h> +#include <linux/preempt.h> #include <linux/delay.h> #include <asm/processor.h> @@ -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 <linux/module.h> #include <linux/sched.h> +#include <linux/preempt.h> #include <linux/delay.h> + #include <asm/delay.h> #include <asm/msr.h> @@ -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); |