Re: [PATCH] 2.5.21 IDE 91

[Linus Torvalds]

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.

		Linus