diff options
| author | Andi Kleen | 2006-11-14 16:57:46 +0100 |
|---|---|---|
| committer | Andi Kleen | 2006-11-14 16:57:46 +0100 |
| commit | 9446868b5383eb87f76b2d4389dea4bb968a6657 (patch) | |
| tree | d253d9a0ae99c77f43ca271019fcbdbfd349b665 | |
| parent | 8c131af1db510793f87dc43edbc8950a35370df3 (diff) | |
[PATCH] x86-64: Fix race in exit_idle
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>
| -rw-r--r-- | arch/x86_64/kernel/process.c | 3 | ||||
| -rw-r--r-- | include/asm-x86_64/pda.h | 9 |
2 files changed, 10 insertions, 2 deletions
diff --git a/arch/x86_64/kernel/process.c b/arch/x86_64/kernel/process.c index 49f7fac6229e..f6226055d53d 100644 --- a/arch/x86_64/kernel/process.c +++ b/arch/x86_64/kernel/process.c @@ -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); } diff --git a/include/asm-x86_64/pda.h b/include/asm-x86_64/pda.h index 14996d962bac..5642634843c4 100644 --- a/include/asm-x86_64/pda.h +++ b/include/asm-x86_64/pda.h @@ -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) |