The patch titled
GTOD: Mark TSC unusable for highres timers
has been added to the -mm tree. Its filename is
gtod-mark-tsc-unusable-for-highres-timers.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: GTOD: Mark TSC unusable for highres timers
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
The TSC is too unstable and unreliable to be used with high resolution timers.
The automatic detection of TSC unstability fails once we switched to high
resolution mode, because the tick emulation would use the TSC as reference.
This results in a circular dependency. Mark it unusable for high res upfront.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
arch/i386/kernel/tsc.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff -puN arch/i386/kernel/tsc.c~gtod-mark-tsc-unusable-for-highres-timers arch/i386/kernel/tsc.c
--- a/arch/i386/kernel/tsc.c~gtod-mark-tsc-unusable-for-highres-timers
+++ a/arch/i386/kernel/tsc.c
@@ -459,10 +459,23 @@ static int __init init_tsc_clocksource(v
current_tsc_khz = tsc_khz;
clocksource_tsc.mult = clocksource_khz2mult(current_tsc_khz,
clocksource_tsc.shift);
+#ifndef CONFIG_HIGH_RES_TIMERS
/* lower the rating if we already know its unstable: */
if (check_tsc_unstable())
clocksource_tsc.rating = 50;
-
+#else
+ /*
+ * Mark TSC unsuitable for high resolution timers. TSC has so
+ * many pitfalls: frequency changes, stop in idle ... When we
+ * switch to high resolution mode we can not longer detect a
+ * firmware caused frequency change, as the emulated tick uses
+ * TSC as reference. This results in a circular dependency.
+ * Switch only to high resolution mode, if pm_timer or such
+ * is available.
+ */
+ clocksource_tsc.rating = 50;
+ clocksource_tsc.is_continuous = 0;
+#endif
init_timer(&verify_tsc_freq_timer);
verify_tsc_freq_timer.function = verify_tsc_freq;
verify_tsc_freq_timer.expires =
_
Patches currently in -mm which might be from tglx@xxxxxxxxxxxxx are
gtod-exponential-update_wall_time.patch
gtod-persistent-clock-support-core.patch
gtod-persistent-clock-support-i386.patch
time-uninline-jiffiesh.patch
time-fix-msecs_to_jiffies-bug.patch
time-fix-timeout-overflow.patch
cleanup-uninline-irq_enter-and-move-it-into-a.patch
dynticks-extend-next_timer_interrupt-to-use-a.patch
hrtimers-namespace-and-enum-cleanup.patch
hrtimers-clean-up-locking.patch
hrtimers-state-tracking.patch
hrtimers-clean-up-callback-tracking.patch
hrtimers-move-and-add-documentation.patch
clockevents-core.patch
clockevents-drivers-for-i386.patch
high-res-timers-core.patch
gtod-mark-tsc-unusable-for-highres-timers.patch
dynticks-core.patch
dyntick-add-nohz-stats-to-proc-stat.patch
dynticks-i386-arch-code.patch
high-res-timers-dynticks-enable-i386-support.patch
debugging-feature-timer-stats.patch
-
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