diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2007-03-24 23:02:49 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@woody.linux-foundation.org> | 2007-03-24 15:45:53 -0700 |
| commit | d9a5c0a4e0b4c84850a1a5bbacba3f7858b67037 (patch) | |
| tree | 5efaefd34302050ef6d530dafc20635c7ad2842b /arch | |
| parent | 8fb303c7f1118b0a82aa08e33429adf9b5ad192c (diff) | |
[PATCH] i386: Prevent early access to TSC to avoid crash on TSCless systems
commit f9690982b8c2f9a2c65acdc113e758ec356676a3 removed the check for
cpu_khz from sched_clock(), which prevented early access to the TSC by
non obvious magic.
This is harmless as long as the CPU has a TSC. On TSCless systems this
results in an illegal instruction trap.
Replace tsc_disabled and tsc_unstable by tsc_enabled, which is only set
when the tsc is available and not unstable.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/i386/kernel/tsc.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/arch/i386/kernel/tsc.c b/arch/i386/kernel/tsc.c index 0e65f7ab63a2..6cb8f5336732 100644 --- a/arch/i386/kernel/tsc.c +++ b/arch/i386/kernel/tsc.c @@ -18,6 +18,8 @@ #include "mach_timer.h" +static int tsc_enabled; + /* * On some systems the TSC frequency does not * change with the cpu frequency. So we need @@ -105,7 +107,7 @@ unsigned long long sched_clock(void) /* * Fall back to jiffies if there's no TSC available: */ - if (tsc_unstable || unlikely(tsc_disable)) + if (unlikely(!tsc_enabled)) /* No locking but a rare wrong value is not a big deal: */ return (jiffies_64 - INITIAL_JIFFIES) * (1000000000 / HZ); @@ -283,6 +285,7 @@ void mark_tsc_unstable(void) { if (!tsc_unstable) { tsc_unstable = 1; + tsc_enabled = 0; /* Can be called before registration */ if (clocksource_tsc.mult) clocksource_change_rating(&clocksource_tsc, 0); @@ -383,7 +386,9 @@ 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); return; |