[PATCH] m68knommu: fix scheduling and race problems in idle loop
Re-work the m68knommu specific idle code according to suggestions
from Nick Piggin <nickpiggin@yahoo.com.au>.
A couple of rules that we need to follow:
1. Preempt should now disabled over idle routines. Should only be enabled
to call schedule() then disabled again.
3. When cpu_idle finds (need_resched() == 'true'), it should call schedule().
It should not call schedule() otherwise.
Also fix interrupt locking around the need_resched() and cpu stop state
so that there is no race condition.
Signed-off-by: Greg Ungerer <gerg@snapgear.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/arch/m68knommu/kernel/process.c b/arch/m68knommu/kernel/process.c
index 2b6c9d3..c4a33f2 100644
--- a/arch/m68knommu/kernel/process.c
+++ b/arch/m68knommu/kernel/process.c
@@ -45,11 +45,13 @@
*/
void default_idle(void)
{
- while(1) {
- if (need_resched())
- __asm__("stop #0x2000" : : : "cc");
- schedule();
+ local_irq_disable();
+ while (!need_resched()) {
+ /* This stop will re-enable interrupts */
+ __asm__("stop #0x2000" : : : "cc");
+ local_irq_disable();
}
+ local_irq_enable();
}
void (*idle)(void) = default_idle;
@@ -63,7 +65,12 @@
void cpu_idle(void)
{
/* endless idle loop with no priority at all */
- idle();
+ while (1) {
+ idle();
+ preempt_enable_no_resched();
+ schedule();
+ preempt_disable();
+ }
}
void machine_restart(char * __unused)