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SubjectRe: 2.6.32.21 - uptime related crashes?
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On Thu, 2011-07-21 at 09:22 +0200, Ingo Molnar wrote:
>
> Ping, what's going on with this bug? Systems are crashing so we need
> a quick fix ASAP ...

Something as simple as the below ought to cure things for now. Once we
get __cycles_2_ns() fixed up we can enable it again.

(patch against -tip, .32 code is different but equally simple to fix)

---
Subject: x86, intel: Don't mark sched_clock() as stable
Because the x86 sched_clock() implementation wraps at 54 bits and the
scheduler code assumes it wraps at the full 64bits we can get into
trouble after 208 days (~7 months) of uptime.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
arch/x86/kernel/cpu/intel.c | 7 +++++++
1 files changed, 7 insertions(+), 0 deletions(-)
diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c
index ed6086e..c8dc48b 100644
--- a/arch/x86/kernel/cpu/intel.c
+++ b/arch/x86/kernel/cpu/intel.c
@@ -91,8 +91,15 @@ static void __cpuinit early_init_intel(struct cpuinfo_x86 *c)
if (c->x86_power & (1 << 8)) {
set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
+ /*
+ * Unfortunately our __cycles_2_ns() implementation makes
+ * the raw sched_clock() interface wrap at 54-bits, which
+ * makes it unsuitable for direct use, so disable this
+ * for now.
+ *
if (!check_tsc_unstable())
sched_clock_stable = 1;
+ */
}

/*


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