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[PATCH] Fix idle notifiers

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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: Andi Kleen <ak@suse.de>
This commit is contained in:
Andi Kleen 2006-09-26 10:52:40 +02:00 committed by Andi Kleen
parent 1c9c0a6ca3
commit a15da49deb
2 changed files with 11 additions and 7 deletions
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15
arch/x86_64/kernel/process.c
View file

@ -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();
}

3
include/asm-x86_64/pda.h
View file

@ -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;