Messages in this thread Patch in this message | | | Date | Tue, 03 Feb 2009 16:01:46 -0800 | From | Jeremy Fitzhardinge <> | Subject | [PATCH] xen: disable interrupts before saving in percpu |
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xen_mc_batch has a small preempt race where it takes the address of a percpu variable immediately before disabling interrupts, thereby leaving a small window in which we may migrate to another cpu and save the flags in the wrong percpu variable. Disable interrupts before saving the old flags in a percpu.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> --- arch/x86/xen/multicalls.h | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
=================================================================== --- a/arch/x86/xen/multicalls.h +++ b/arch/x86/xen/multicalls.h @@ -19,8 +19,10 @@ paired with xen_mc_issue() */ static inline void xen_mc_batch(void) { + unsigned long flags; /* need to disable interrupts until this entry is complete */ - local_irq_save(__get_cpu_var(xen_mc_irq_flags)); + local_irq_save(flags); + __get_cpu_var(xen_mc_irq_flags) = flags; } static inline struct multicall_space xen_mc_entry(size_t args)
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