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Commit a15da49d authored by Andi Kleen's avatar Andi Kleen Committed by Andi Kleen
Browse files

[PATCH] Fix idle notifiers 



Previously exit_idle would be called more often than enter_idle

Now instead of using complicated tests just keep track of it
using the per CPU variable as a flip flop.  I moved the idle state into the
PDA to make the access more efficient.

Original bug report and an initial patch from Stephane Eranian,
but redone by AK.

Cc: Stephane Eranian <eranian@hpl.hp.com>

Signed-off-by: default avatarAndi Kleen <ak@suse.de>
parent 1c9c0a6c

arch/x86_64/kernel/process.c

+9 −6
Original line number Diff line number Diff line
@@ -80,25 +80,25 @@ void idle_notifier_unregister(struct notifier_block *n) 
}

EXPORT_SYMBOL(idle_notifier_unregister);



enum idle_state { CPU_IDLE, CPU_NOT_IDLE };

static DEFINE_PER_CPU(enum idle_state, idle_state) = CPU_NOT_IDLE;



void enter_idle(void)

{

	__get_cpu_var(idle_state) = CPU_IDLE;

	write_pda(isidle, 1);

	atomic_notifier_call_chain(&idle_notifier, IDLE_START, NULL);

}



static void __exit_idle(void)

{

	__get_cpu_var(idle_state) = CPU_NOT_IDLE;

	if (read_pda(isidle) == 0)

		return;

	write_pda(isidle, 0);

	atomic_notifier_call_chain(&idle_notifier, IDLE_END, NULL);

}



/* Called from interrupts to signify idle end */

void exit_idle(void)

{

	if (current->pid | read_pda(irqcount))

	/* idle loop has pid 0 */

	if (current->pid)

		return;

	__exit_idle();

}
@@ -220,6 +220,9 @@ void cpu_idle (void) 
				play_dead();

			enter_idle();

			idle();

			/* In many cases the interrupt that ended idle

			   has already called exit_idle. But some idle

			   loops can be woken up without interrupt. */

			__exit_idle();

		}

include/asm-x86_64/pda.h

+2 −1
Original line number Diff line number Diff line
@@ -25,7 +25,8 @@ struct x8664_pda { 
	int nodenumber;		    /* number of current node */

	unsigned int __softirq_pending;

	unsigned int __nmi_count;	/* number of NMI on this CPUs */

	int mmu_state;     

	short mmu_state;

	short isidle;

	struct mm_struct *active_mm;

	unsigned apic_timer_irqs;

} ____cacheline_aligned_in_smp;