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Date: Sun, 3 Nov 2002 16:39:06 -0800
From: William Lee Irwin III <wli@holomorphy.com>
To: Davide Libenzi <davidel@xmailserver.org>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, hch@lst.de,
       Benjamin LaHaise <bcrl@redhat.com>
Subject: Re: interrupt checks for spinlocks
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On Sun, 3 Nov 2002, William Lee Irwin III wrote:
[...]
>> The only action taken is printk() and dump_stack(). No arch code has
>> been futzed with to provide irq tainting yet. Looks like a good way
>> to shake out lurking bugs to me (somewhat like may_sleep() etc.).

On Sun, Nov 03, 2002 at 04:15:46PM -0800, Davide Libenzi wrote:
> Wouldn't it be interesting to keep a ( per task ) list of acquired
> spinlocks to be able to diagnose cross locks in case of stall ?
> ( obviously under CONFIG_DEBUG_SPINLOCK )

That would appear to require cycle detection, but it sounds like a
potential breakthrough usage of graph algorithms in the kernel.
(I've always been told graph algorithms would come back to haunt me.)
Or maybe not, deadlock detection has been done before.

A separate patch/feature/whatever for deadlock detection could do that
nicely, though. What I've presented here is meant only to flag far more
trivial errors with interrupt enablement/disablement than the full
deadlock detection problem.


Bill
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