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authorjohn stultz <johnstul@us.ibm.com>2006-10-17 00:09:32 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-10-17 08:18:42 -0700
commit3f4a0b917ce72ef47e438d354c433eb645218e87 (patch)
tree82695f890785cfe1bd14303ce04453a16bd99c01 /kernel
parentb9f5d8040b470e4f74e3266ece2969ef06d0f8aa (diff)
[PATCH] i386 Time: Avoid PIT SMP lockups
Avoid possible PIT livelock issues seen on SMP systems (and reported by Andi), by not allowing it as a clocksource on SMP boxes. However, since the PIT may no longer be present, we have to properly handle the cases where SMP systems have TSC skew and fall back from the TSC. Since the PIT isn't there, it would "fall back" to the TSC again. So this changes the jiffies rating to 1, and the TSC-bad rating value to 0. Thus you will get the following behavior priority on i386 systems: tsc [if present & stable] hpet [if present] cyclone [if present] acpi_pm [if present] pit [if UP] jiffies Rather then the current more complicated: tsc [if present & stable] hpet [if present] cyclone [if present] acpi_pm [if present] pit [if cpus < 4] tsc [if present & unstable] jiffies Signed-off-by: John Stultz <johnstul@us.ibm.com> Cc: Andi Kleen <ak@suse.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/time/jiffies.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/time/jiffies.c b/kernel/time/jiffies.c
index 126bb30c4af..a99b2a6e6a0 100644
--- a/kernel/time/jiffies.c
+++ b/kernel/time/jiffies.c
@@ -57,7 +57,7 @@ static cycle_t jiffies_read(void)
struct clocksource clocksource_jiffies = {
.name = "jiffies",
- .rating = 0, /* lowest rating*/
+ .rating = 1, /* lowest valid rating*/
.read = jiffies_read,
.mask = 0xffffffff, /*32bits*/
.mult = NSEC_PER_JIFFY << JIFFIES_SHIFT, /* details above */