Re: [PATCH][BUG] Badness in smp_call_function at arch/i386/kernel/smp.c:552

[Zwane Mwaikambo]

On Thu, 2 Dec 2004, Andrew Morton wrote:

> >  > However enabling interrupts as you've done menas that theoretically we
> >  > could deadlock on sysrq_key_table_lock if another sysrq happens at the
> >  > wrong time.
> >  > 
> >  > Which deadlock opportunity would you prefer? ;)
> > 
> >  Agreed, there is actually a higher chance of the smp_call_function 
> >  deadlock occuring since the __handle_sysrq one relies on another sysrq 
> >  event occuring via a different IRQ line interrupt handler, so 
> >  we would have to do sysrq via serial and then sysrq via keyboard to cause 
> >  the deadlock. Perhaps just make it a spin_trylock?
> 
> Well yeah, but it's so much fuss for such a silly problem.
> 
> How about a local_irq_enable() in sysrq_handle_reboot()?

That should be fine too, i prefer it to local_irq_enable in 
machine_shutdown() too.

Signed-off-by: Zwane Mwaikambo <zwane@xxxxxxxxxxxxxx>

===== drivers/char/sysrq.c 1.32 vs edited =====
--- 1.32/drivers/char/sysrq.c	2004-11-07 19:13:54 -07:00
+++ edited/drivers/char/sysrq.c	2004-12-03 00:42:29 -07:00
@@ -98,6 +98,7 @@ static struct sysrq_key_op sysrq_unraw_o
 static void sysrq_handle_reboot(int key, struct pt_regs *pt_regs,
 				struct tty_struct *tty) 
 {
+	local_irq_enable();
 	machine_restart(NULL);
 }
 
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