The patch titled
i386: prevent early access to TSC to avoid crash on TSCless systems
has been added to the -mm tree. Its filename is
i386-prevent-early-access-to-tsc-to-avoid-crash-on.patch
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: i386: prevent early access to TSC to avoid crash on TSCless systems
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Acked-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
arch/i386/kernel/tsc.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff -puN arch/i386/kernel/tsc.c~i386-prevent-early-access-to-tsc-to-avoid-crash-on arch/i386/kernel/tsc.c
--- a/arch/i386/kernel/tsc.c~i386-prevent-early-access-to-tsc-to-avoid-crash-on
+++ a/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;
_
Patches currently in -mm which might be from tglx@xxxxxxxxxxxxx are
origin.patch
time-fix-formatting-in-proc-timer_list.patch
correct-slow-acpi_pm-rating.patch
i386-prevent-early-access-to-tsc-to-avoid-crash-on.patch
git-ieee1394.patch
log-reason-why-tsc-was-marked-unstable.patch
optimize-timespec_trunc.patch
sched-fix-idle-load-balancing-in-softirqd-context.patch
sched-dynticks-idle-load-balancing-v3.patch
mm-only-hrtimers-debug-patch.patch
-
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
