[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: Andi Kleen <ak@suse.de>
diff --git a/arch/x86_64/kernel/process.c b/arch/x86_64/kernel/process.c
index 885c318..458006a 100644
--- a/arch/x86_64/kernel/process.c
+++ b/arch/x86_64/kernel/process.c
@@ -80,25 +80,25 @@
}
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 @@
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();
}
diff --git a/include/asm-x86_64/pda.h b/include/asm-x86_64/pda.h
index 531f48a..14996d9 100644
--- a/include/asm-x86_64/pda.h
+++ b/include/asm-x86_64/pda.h
@@ -25,7 +25,8 @@
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;