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Subject[PATCH] preempt-safe load_LDT
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Linus,

Attached patch makes load_LDT preempt-safe per our off-list discussion.

Header dependencies prevent use of the get_cpu()/put_cpu() methods so we
explicitly call disable/enable.

This is Ingo Molnar's version of the patch: I like how he broke up
load_LDT into two versions better.

Patch is against 2.5.27, please apply.

Robert Love

diff -urN linux-2.5.27/include/asm-i386/desc.h linux/include/asm-i386/desc.h
--- linux-2.5.27/include/asm-i386/desc.h Sat Jul 20 12:11:03 2002
+++ linux/include/asm-i386/desc.h Sat Jul 20 12:48:15 2002
@@ -90,9 +90,8 @@
/*
* load one particular LDT into the current CPU
*/
-static inline void load_LDT (mm_context_t *pc)
+static inline void load_LDT_no_preempt(mm_context_t *pc, int cpu)
{
- int cpu = smp_processor_id();
void *segments = pc->ldt;
int count = pc->size;

@@ -104,6 +103,14 @@
set_ldt_desc(cpu, segments, count);
__load_LDT(cpu);
}
+static inline void load_LDT(mm_context_t *pc)
+{
+ int cpu = smp_processor_id();
+
+ preempt_disable();
+ load_LDT_no_preempt(pc, cpu);
+ preempt_enable();
+}

#endif /* !__ASSEMBLY__ */

diff -urN linux-2.5.27/include/asm-i386/mmu_context.h linux/include/asm-i386/mmu_context.h
--- linux-2.5.27/include/asm-i386/mmu_context.h Sat Jul 20 12:11:04 2002
+++ linux/include/asm-i386/mmu_context.h Sat Jul 20 12:48:15 2002
@@ -44,7 +44,7 @@
* has a non-default LDT.
*/
if (next->context.size+prev->context.size)
- load_LDT(&next->context);
+ load_LDT_no_preempt(&next->context, cpu);
}
#ifdef CONFIG_SMP
else {
@@ -56,7 +56,7 @@
* tlb flush IPI delivery. We must reload %cr3.
*/
load_cr3(next->pgd);
- load_LDT(&next->context);
+ load_LDT_no_preempt(&next->context, cpu);
}
}
#endif
-
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