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[PATCH] x86_64: Fix race in TSC synchronization

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Plug a race in TSC synchronization

We need to do tsc_sync_wait() before the CPU is set online to prevent
multiple CPUs from doing it in parallel - which won't work because TSC
sync has global unprotected state.

Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Andi Kleen
2005-08-19 06:56:40 +02:00
committed by Linus Torvalds
parent 5e5ec10499
commit 1eecd73cce
1 changed files with 8 additions and 7 deletions
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15
arch/x86_64/kernel/smpboot.c
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@@ -492,6 +492,14 @@ void __cpuinit start_secondary(void)
*/ */
set_cpu_sibling_map(smp_processor_id()); set_cpu_sibling_map(smp_processor_id());
/*
* Wait for TSC sync to not schedule things before.
* We still process interrupts, which could see an inconsistent
* time in that window unfortunately.
* Do this here because TSC sync has global unprotected state.
*/
tsc_sync_wait();
/* /*
* We need to hold call_lock, so there is no inconsistency * We need to hold call_lock, so there is no inconsistency
* between the time smp_call_function() determines number of * between the time smp_call_function() determines number of
@@ -509,13 +517,6 @@ void __cpuinit start_secondary(void)
per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE; per_cpu(cpu_state, smp_processor_id()) = CPU_ONLINE;
unlock_ipi_call_lock(); unlock_ipi_call_lock();
mb();
/* Wait for TSC sync to not schedule things before.
We still process interrupts, which could see an inconsistent
time in that window unfortunately. */
tsc_sync_wait();
cpu_idle(); cpu_idle();
} }