Hello.
Thomas Gleixner wrote:
>
> The patch prevents this by leaving interrupts disabled and calling
> a seperate function preempt_schedule_irq().
sched-fix-preemption-race-core-i386.patch:
>
> +++ 25-akpm/arch/i386/kernel/entry.S
> @@ -189,6 +189,7 @@ ENTRY(resume_userspace)
>
> #ifdef CONFIG_PREEMPT
> ENTRY(resume_kernel)
> + cli
I think this 'cli' is unneeded. resume_kernel: is used on
return path from do_IRQ() which leaves interrupts disabled.
irq_desc->handler->end() should not enable interrupts, yes?
And we have preempt_stop==cli in ret_from_exception: case,
before ret_from_intr.
> +++ 25-akpm/kernel/sched.c
> @@ -2872,6 +2872,48 @@ need_resched:
> ...
> +asmlinkage void __sched preempt_schedule_irq(void)
> +{
> ...
> + local_irq_enable();
> + schedule();
It is ok to enter schedule() with interrupts disabled, so this
'sti' seems to be unneeded too.
Am I missed something?
Signed-off-by: Oleg Nesterov <[EMAIL PROTECTED]>
--- 2.6.11-rc2-mm2/arch/i386/kernel/entry.S~ Mon Jan 31 14:09:37 2005
+++ 2.6.11-rc2-mm2/arch/i386/kernel/entry.S Mon Jan 31 14:55:25 2005
@@ -189,7 +189,6 @@ ENTRY(resume_userspace)
#ifdef CONFIG_PREEMPT
ENTRY(resume_kernel)
- cli
cmpl $0,TI_preempt_count(%ebp) # non-zero preempt_count ?
jnz restore_all
need_resched:
--- 2.6.11-rc2-mm2/kernel/sched.c~ Mon Jan 31 14:09:54 2005
+++ 2.6.11-rc2-mm2/kernel/sched.c Mon Jan 31 14:57:44 2005
@@ -2971,7 +2971,6 @@ need_resched:
saved_lock_depth = task->lock_depth;
task->lock_depth = -1;
#endif
- local_irq_enable();
schedule();
local_irq_disable();
#ifdef CONFIG_PREEMPT_BKL
-
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