diff options
Diffstat (limited to 'arch/x86/kernel/tsc_32.c')
| -rw-r--r-- | arch/x86/kernel/tsc_32.c | 23 |
1 files changed, 13 insertions, 10 deletions
diff --git a/arch/x86/kernel/tsc_32.c b/arch/x86/kernel/tsc_32.c index e4790728b22..65b70637ad9 100644 --- a/arch/x86/kernel/tsc_32.c +++ b/arch/x86/kernel/tsc_32.c @@ -14,7 +14,10 @@ #include "mach_timer.h" -static int tsc_enabled; +/* native_sched_clock() is called before tsc_init(), so + we must start with the TSC soft disabled to prevent + erroneous rdtsc usage on !cpu_has_tsc processors */ +static int tsc_disabled = -1; /* * On some systems the TSC frequency does not @@ -28,8 +31,8 @@ EXPORT_SYMBOL_GPL(tsc_khz); static int __init tsc_setup(char *str) { printk(KERN_WARNING "notsc: Kernel compiled with CONFIG_X86_TSC, " - "cannot disable TSC completely.\n"); - mark_tsc_unstable("user disabled TSC"); + "cannot disable TSC completely.\n"); + tsc_disabled = 1; return 1; } #else @@ -120,7 +123,7 @@ unsigned long long native_sched_clock(void) * very important for it to be as fast as the platform * can achive it. ) */ - if (unlikely(!tsc_enabled && !tsc_unstable)) + if (unlikely(tsc_disabled)) /* No locking but a rare wrong value is not a big deal: */ return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ); @@ -322,7 +325,6 @@ void mark_tsc_unstable(char *reason) { if (!tsc_unstable) { tsc_unstable = 1; - tsc_enabled = 0; printk("Marking TSC unstable due to: %s.\n", reason); /* Can be called before registration */ if (clocksource_tsc.mult) @@ -336,7 +338,7 @@ EXPORT_SYMBOL_GPL(mark_tsc_unstable); static int __init dmi_mark_tsc_unstable(const struct dmi_system_id *d) { printk(KERN_NOTICE "%s detected: marking TSC unstable.\n", - d->ident); + d->ident); tsc_unstable = 1; return 0; } @@ -403,7 +405,7 @@ void __init tsc_init(void) { int cpu; - if (!cpu_has_tsc) + if (!cpu_has_tsc || tsc_disabled > 0) return; cpu_khz = calculate_cpu_khz(); @@ -414,6 +416,9 @@ void __init tsc_init(void) return; } + /* now allow native_sched_clock() to use rdtsc */ + tsc_disabled = 0; + printk("Detected %lu.%03lu MHz processor.\n", (unsigned long)cpu_khz / 1000, (unsigned long)cpu_khz % 1000); @@ -441,8 +446,6 @@ void __init tsc_init(void) if (check_tsc_unstable()) { clocksource_tsc.rating = 0; clocksource_tsc.flags &= ~CLOCK_SOURCE_IS_CONTINUOUS; - } else - tsc_enabled = 1; - + } clocksource_register(&clocksource_tsc); } |