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authorJan Beulich <JBeulich@novell.com>2011-07-19 11:39:03 +0100
committerIngo Molnar <mingo@elte.hu>2011-07-21 09:20:59 +0200
commitac619f4eba45da10053fc991f8a5d47b3be79fa3 (patch)
treec1abddc5657dd6efa9a8e8ed2fb4303bd01643dc
parent7e794cb7e36ccdb8c44b8ca7738720625b7aa2da (diff)
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x86: Serialize SMP bootup CMOS accesses on rtc_lock
With CPU hotplug, there is a theoretical race between other CMOS (namely RTC) accesses and those done in the SMP secondary processor bringup path. I am unware of the problem having been noticed by anyone in practice, but it would very likely be rather spurious and very hard to reproduce. So to be on the safe side, acquire rtc_lock around those accesses. Signed-off-by: Jan Beulich <jbeulich@novell.com> Cc: John Stultz <john.stultz@linaro.org> Link: http://lkml.kernel.org/r/4E257AE7020000780004E2FF@nat28.tlf.novell.com Signed-off-by: Ingo Molnar <mingo@elte.hu>
-rw-r--r--arch/x86/include/asm/smpboot_hooks.h8
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/x86/include/asm/smpboot_hooks.h b/arch/x86/include/asm/smpboot_hooks.h
index 725b7783199..49adfd7bb4a 100644
--- a/arch/x86/include/asm/smpboot_hooks.h
+++ b/arch/x86/include/asm/smpboot_hooks.h
@@ -10,7 +10,11 @@ static inline void smpboot_clear_io_apic_irqs(void)
static inline void smpboot_setup_warm_reset_vector(unsigned long start_eip)
{
+ unsigned long flags;
+
+ spin_lock_irqsave(&rtc_lock, flags);
CMOS_WRITE(0xa, 0xf);
+ spin_unlock_irqrestore(&rtc_lock, flags);
local_flush_tlb();
pr_debug("1.\n");
*((volatile unsigned short *)phys_to_virt(apic->trampoline_phys_high)) =
@@ -23,6 +27,8 @@ static inline void smpboot_setup_warm_reset_vector(unsigned long start_eip)
static inline void smpboot_restore_warm_reset_vector(void)
{
+ unsigned long flags;
+
/*
* Install writable page 0 entry to set BIOS data area.
*/
@@ -32,7 +38,9 @@ static inline void smpboot_restore_warm_reset_vector(void)
* Paranoid: Set warm reset code and vector here back
* to default values.
*/
+ spin_lock_irqsave(&rtc_lock, flags);
CMOS_WRITE(0, 0xf);
+ spin_unlock_irqrestore(&rtc_lock, flags);
*((volatile u32 *)phys_to_virt(apic->trampoline_phys_low)) = 0;
}