diff options
Diffstat (limited to 'arch/x86/lib/delay_64.c')
| -rw-r--r-- | arch/x86/lib/delay_64.c | 30 |
1 files changed, 26 insertions, 4 deletions
diff --git a/arch/x86/lib/delay_64.c b/arch/x86/lib/delay_64.c index bbc610518516..4c441be92641 100644 --- a/arch/x86/lib/delay_64.c +++ b/arch/x86/lib/delay_64.c @@ -31,14 +31,36 @@ int __devinit read_current_timer(unsigned long *timer_value) void __delay(unsigned long loops) { unsigned bclock, now; + int cpu; - preempt_disable(); /* TSC's are pre-cpu */ + preempt_disable(); + cpu = smp_processor_id(); rdtscl(bclock); - do { - rep_nop(); + for (;;) { rdtscl(now); + if ((now - bclock) >= loops) + break; + + /* 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())) { + loops -= (now - bclock); + cpu = smp_processor_id(); + rdtscl(bclock); + } } - while ((now-bclock) < loops); preempt_enable(); } EXPORT_SYMBOL(__delay); |