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Date: Fri, 14 Jun 2002 09:43:11 -0700 (PDT)
From: Linus Torvalds <torvalds@transmeta.com>
To: Jens Axboe <axboe@suse.de>
cc: Martin Dalecki <dalecki@evision-ventures.com>,
        Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] 2.5.21 IDE 91
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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

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