diff options
Diffstat (limited to 'arch/i386/kernel/tsc.c')
| -rw-r--r-- | arch/i386/kernel/tsc.c | 26 |
1 files changed, 18 insertions, 8 deletions
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c index 2cfc7b09b92..46f752a8bbf 100644 --- a/arch/i386/kernel/tsc.c +++ b/arch/i386/kernel/tsc.c @@ -23,6 +23,7 @@ * an extra value to store the TSC freq */ unsigned int tsc_khz; +unsigned long long (*custom_sched_clock)(void); int tsc_disable; @@ -107,14 +108,14 @@ unsigned long long sched_clock(void) { unsigned long long this_offset; + if (unlikely(custom_sched_clock)) + return (*custom_sched_clock)(); + /* - * in the NUMA case we dont use the TSC as they are not - * synchronized across all CPUs. + * Fall back to jiffies if there's no TSC available: */ -#ifndef CONFIG_NUMA - if (!cpu_khz || check_tsc_unstable()) -#endif - /* no locking but a rare wrong value is not a big deal */ + if (unlikely(tsc_disable)) + /* No locking but a rare wrong value is not a big deal: */ return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ); /* read the Time Stamp Counter: */ @@ -194,13 +195,13 @@ EXPORT_SYMBOL(recalibrate_cpu_khz); void __init tsc_init(void) { if (!cpu_has_tsc || tsc_disable) - return; + goto out_no_tsc; cpu_khz = calculate_cpu_khz(); tsc_khz = cpu_khz; if (!cpu_khz) - return; + goto out_no_tsc; printk("Detected %lu.%03lu MHz processor.\n", (unsigned long)cpu_khz / 1000, @@ -208,6 +209,15 @@ void __init tsc_init(void) set_cyc2ns_scale(cpu_khz); use_tsc_delay(); + return; + +out_no_tsc: + /* + * Set the tsc_disable flag if there's no TSC support, this + * makes it a fast flag for the kernel to see whether it + * should be using the TSC. + */ + tsc_disable = 1; } #ifdef CONFIG_CPU_FREQ |