Re: [PATCH] 2.5.21 IDE 91

[Jens Axboe <axboe@suse.de>]

On Fri, Jun 14 2002, Linus Torvalds wrote:
> 
> 
> On Fri, 14 Jun 2002, Jens Axboe wrote:
> >
> > - current 2.5 bk deadlocks reading partition info off disk. Again a
> >   locking problem I suppose, to be honest I just got very tired when
> >   seeing it happen and didn't want to spend tim looking into it.
> 
> Hmm. There's a bug in "balance_irq()" if you are trying to run a SMP
> kernel on an UP machine right now, and it _might_ be that the lockup has
> nothing to do with the IDE layer, but simple with the first PCI interrupt
> (as opposed to local timer interrupt) coming in.
> 
> One-liner from Zwane Mwaikambo (cut-and-paste, so space is wrong, please
> apply by hand).
> 
> --- linux-2.5.19/arch/i386/kernel/io_apic.c.orig        Fri Jun 14 17:43:20 2002
> +++ linux-2.5.19/arch/i386/kernel/io_apic.c     Fri Jun 14 17:42:23 2002
> @@ -251,7 +251,7 @@
>         irq_balance_t *entry = irq_balance + irq;
>         unsigned long now = jiffies;
> 
> -       if (unlikely(entry->timestamp != now)) {
> +       if ((entry->timestamp != now) && (smp_num_cpus > 1)) {
>                 unsigned long allowed_mask;
>                 int random_number;
> 
> I don't know. Might be the IDE code too, of course.

If it's just a SMP kernel on UP, then that's not the problem here. This
was SMP kernel on SMP machine.

-- 
Jens Axboe