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42 lines
1.6 KiB
Diff
42 lines
1.6 KiB
Diff
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From: Dimitri Sivanich <sivanich@sgi.com>
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Subject: x86: Fix sched_clock_cpu for systems with unsynchronized TSC
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Patch-mainline: not yet
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References: bnc#582878, FATE#306952
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Patch-mainline: not yet
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On UV systems, the TSC is not synchronized across blades. The
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sched_clock_cpu() function is returning values that can go
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backwards (I've seen as much as 8 seconds) when switching
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between cpus.
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As each cpu comes up, early_init_intel() will currently set the
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sched_clock_stable flag true. When mark_tsc_unstable() runs, it
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clears the flag, but this only occurs once (the first time a cpu
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comes up whose TSC is not synchronized with cpu 0). After this,
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early_init_intel() will set the flag again as the next cpu comes
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up.
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Only set sched_clock_stable if tsc has not been marked unstable.
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Signed-off-by: Dimitri Sivanich <sivanich@sgi.com>
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Acked-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
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Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
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LKML-Reference: <20100301174815.GC8224@sgi.com>
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Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Signed-off-by: Rafael J. Wysocki <rjw@suse.de>
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Automatically created from "patches.arch/x86-Fix-sched_clock_cpu-for-systems-with-unsynchronized-TSC.patch" by xen-port-patches.py
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--- sle11sp1-2010-03-11.orig/arch/x86/kernel/cpu/intel.c 2010-03-11 09:10:10.000000000 +0100
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+++ sle11sp1-2010-03-11/arch/x86/kernel/cpu/intel.c 2010-03-11 09:32:53.000000000 +0100
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@@ -70,7 +70,9 @@ static void __cpuinit early_init_intel(s
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if (c->x86_power & (1 << 8)) {
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set_cpu_cap(c, X86_FEATURE_CONSTANT_TSC);
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set_cpu_cap(c, X86_FEATURE_NONSTOP_TSC);
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+#ifndef CONFIG_XEN
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if (!check_tsc_unstable())
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+#endif
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sched_clock_stable = 1;
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}
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