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Diffstat (limited to 'arch/i386/kernel/tsc.c')
-rw-r--r--arch/i386/kernel/tsc.c26
1 files changed, 18 insertions, 8 deletions
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c
index 2cfc7b09b925..46f752a8bbf3 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