Commit 9446868b authored by Andi Kleen's avatar Andi Kleen Committed by Andi Kleen

[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: default avatarAndi Kleen <ak@suse.de>
parent 8c131af1
......@@ -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);
}
......
......@@ -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)
......
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