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Commit d331e739 authored by Venkatesh Pallipadi's avatar Venkatesh Pallipadi Committed by Andi Kleen
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[PATCH] x86-64: Fix interrupt race in idle callback (3rd try) 



Idle callbacks has some races when enter_idle() sets isidle and subsequent
interrupts that can happen on that CPU, before CPU goes to idle. Due to this,
an IDLE_END can get called before IDLE_START. To avoid these races, disable
interrupts before enter_idle and make sure that all idle routines do not
enable interrupts before entering idle.

Note that poll_idle() still has a this race as it has to enable interrupts
before going to idle. But, all other idle routines have the race fixed.

Signed-off-by: default avatarVenkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
parent a0429d0d

arch/x86_64/kernel/process.c

+17 −2
Original line number Diff line number Diff line
@@ -127,6 +127,7 @@ static void default_idle(void) 
 */

static void poll_idle (void)

{

	local_irq_enable();

	cpu_relax();

}
@@ -208,6 +209,12 @@ void cpu_idle (void) 
				idle = default_idle;

			if (cpu_is_offline(smp_processor_id()))

				play_dead();

			/*

			 * Idle routines should keep interrupts disabled

			 * from here on, until they go to idle.

			 * Otherwise, idle callbacks can misfire.

			 */

			local_irq_disable();

			enter_idle();

			idle();

			/* In many cases the interrupt that ended idle
@@ -245,8 +252,16 @@ void mwait_idle_with_hints(unsigned long eax, unsigned long ecx) 
/* Default MONITOR/MWAIT with no hints, used for default C1 state */

static void mwait_idle(void)

{

	if (!need_resched()) {

		__monitor((void *)&current_thread_info()->flags, 0, 0);

		smp_mb();

		if (!need_resched())

			__sti_mwait(0, 0);

		else

			local_irq_enable();

	mwait_idle_with_hints(0,0);

	} else {

		local_irq_enable();

	}

}



void __cpuinit select_idle_routine(const struct cpuinfo_x86 *c)

include/asm-x86_64/processor.h

+8 −0
Original line number Diff line number Diff line
@@ -475,6 +475,14 @@ static inline void __mwait(unsigned long eax, unsigned long ecx) 
		: :"a" (eax), "c" (ecx));

}



static inline void __sti_mwait(unsigned long eax, unsigned long ecx)

{

	/* "mwait %eax,%ecx;" */

	asm volatile(

		"sti; .byte 0x0f,0x01,0xc9;"

		: :"a" (eax), "c" (ecx));

}



extern void mwait_idle_with_hints(unsigned long eax, unsigned long ecx);



#define stack_current() \