On Sun, 25 May 2008, Steven Rostedt wrote:
>
> ---
> arch/x86/lib/delay_32.c | 32 ++++++++++++++++++++++++++++----
> arch/x86/lib/delay_64.c | 31 +++++++++++++++++++++++++++----
> 2 files changed, 55 insertions(+), 8 deletions(-)
>
> Index: linux-tip.git/arch/x86/lib/delay_32.c
> ===================================================================
> --- linux-tip.git.orig/arch/x86/lib/delay_32.c 2008-05-22 14:51:02.000000000 -0400
> +++ linux-tip.git/arch/x86/lib/delay_32.c 2008-05-25 09:45:24.000000000 -0400
> @@ -44,13 +44,37 @@ static void delay_loop(unsigned long loo
> static void delay_tsc(unsigned long loops)
> {
> unsigned long bclock, now;
> + int cpu;
>
> - preempt_disable(); /* TSC's are per-cpu */
> + preempt_disable();
> + cpu = smp_processor_id();
> rdtscl(bclock);
> - do {
> - rep_nop();
> + for (;;) {
> rdtscl(now);
> - } while ((now-bclock) < loops);
> + if ((now - bclock) >= loops)
> + break;
> +
> + loops -= (now - bclock);
Bah, this is mathematically incorrect. Going for -v4!
A simple patch like this shouldn't take so much. I must need more sleep.
-- Steve
> +
> + /* Allow RT tasks to run */
> + preempt_enable();
> + rep_nop();
> + preempt_disable();
> +
> + /*
> + * It is possible that we moved to another CPU, and
> + * since TSC's are per-cpu we need to calculate
> + * that. The delay must guarantee that we wait "at
> + * least" the amount of time. Being moved to another
> + * CPU could make the wait longer but we just need to
> + * make sure we waited long enough. Rebalance the
> + * counter for this CPU.
> + */
> + if (unlikely(cpu != smp_processor_id())) {
> + cpu = smp_processor_id();
> + rdtscl(bclock);
> + }
> + }
> preempt_enable();
> }
>
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