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[PATCH] x86-64: Fix race in exit_idle

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When another interrupt happens in exit_idle the exit idle notifier
could be called an incorrect number of times.

Add a test_and_clear_bit_pda and use it handle the bit
atomically against interrupts to avoid this.

Pointed out by Stephane Eranian

Signed-off-by: Andi Kleen <ak@suse.de>
This commit is contained in:
Andi Kleen 2006-11-14 16:57:46 +01:00 committed by Andi Kleen
parent 8c131af1db
commit 9446868b53
2 changed files with 10 additions and 2 deletions
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3
arch/x86_64/kernel/process.c
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@ -88,9 +88,8 @@ void enter_idle(void)
static void __exit_idle(void)
{
if (read_pda(isidle) == 0)
if (test_and_clear_bit_pda(0, isidle) == 0)
return;
write_pda(isidle, 0);
atomic_notifier_call_chain(&idle_notifier, IDLE_END, NULL);
}

9
include/asm-x86_64/pda.h
View File

@ -109,6 +109,15 @@ extern struct x8664_pda _proxy_pda;
#define sub_pda(field,val) pda_to_op("sub",field,val)
#define or_pda(field,val) pda_to_op("or",field,val)
/* This is not atomic against other CPUs -- CPU preemption needs to be off */
#define test_and_clear_bit_pda(bit,field) ({ \
int old__; \
asm volatile("btr %2,%%gs:%c3\n\tsbbl %0,%0" \
: "=r" (old__), "+m" (_proxy_pda.field) \
: "dIr" (bit), "i" (pda_offset(field)) : "memory"); \
old__; \
})
#endif
#define PDA_STACKOFFSET (5*8)