Re: [patch 1/16] unplugging fix

[Andrew Morton <akpm@zip.com.au>]

Andrew Morton wrote:
> 
> There's a plugging bug in 2.5.19.  Once you start pushing several disks
> hard, the new unplug code gets confused and queues are left in plugged
> state, but not on the plug list.  They never get unplugged and the
> machine dies mysteriously.
> 

This patch didn't fix it.  It made it tons better, but I again have a
wedged box.  Same symptoms - against IDE this time.

blk_plug_list is empty.  queue_flags=0x03.  Interestingly,
q->plug_list is non-empty, non-zero, both list members pointing at
a list which isn't either itself or blk_plug_list.

I note that the code isn't taking queues off the plug list when the queue
is destroyed.  Guess that doesn't matter - we never destroy a plugged
queue...

This one is killing me.

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