On Thu, Mar 09, 2006 at 02:21:48AM -0700, Eric W. Biederman wrote:
> Maneesh Soni <[EMAIL PROTECTED]> writes:
>
> > Following was observed by David Wilder while testig kexec on panic on
> > a system with Pentium 4 with HT. Looks like the problem might have
> > occured due to CPU0 holding the lock and then it might have
> > received the NMI and it was stopped with runq lock held. CPU1,
> > enabled the interrupts after stopping other CPU0. Somehow it received
> > the local apic timer interrupt and started spinning on runq lock.
> >
> > Appended is the possible fix for this race condition, which avoids
> > re-enabling irqs on panic shutdown
>
> Grumble. We should not be disabling apics in the first place
> Grumble.
>
Agreed!!
> It is probably better to save and restore the irq state
> in lapic_shutdown(). Than to open code it.
>
I hope this looks ok.
Thanks
Maneesh
o lapic_shutdown() re-enables which is un-desirable for panic case,
so use local_irq_save() and local_irq_restore() to keep the irqs
disabled for kexec on panic case, and close a possible race window.
Signed-off-by: Maneesh Soni <[EMAIL PROTECTED]>
---
linux-2.6.16-rc5-git14-maneesh/arch/i386/kernel/apic.c | 6 ++++--
1 files changed, 4 insertions(+), 2 deletions(-)
diff -puN arch/i386/kernel/apic.c~kdump-shutdown-hang-fix
arch/i386/kernel/apic.c
--- linux-2.6.16-rc5-git14/arch/i386/kernel/apic.c~kdump-shutdown-hang-fix
2006-03-10 17:42:48.473188808 +0530
+++ linux-2.6.16-rc5-git14-maneesh/arch/i386/kernel/apic.c 2006-03-10
17:43:40.390296208 +0530
@@ -570,16 +570,18 @@ void __devinit setup_local_APIC(void)
*/
void lapic_shutdown(void)
{
+ unsigned long flags;
+
if (!cpu_has_apic)
return;
- local_irq_disable();
+ local_irq_save(flags);
clear_local_APIC();
if (enabled_via_apicbase)
disable_local_APIC();
- local_irq_enable();
+ local_irq_restore(flags);
}
#ifdef CONFIG_PM
_
--
Maneesh Soni
Linux Technology Center,
IBM India Software Labs,
Bangalore, India
email: [EMAIL PROTECTED]
Phone: 91-80-51776416
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