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SubjectIDE lockups with 2.5.28...
Martin,
can you explain what local_irq_disable() in do_request in
drivers/ide/ide.c should guard against? There is dozen (all unless I
missed something) of paths which do not local_irq_enable(), and neither
does the caller...

And what you meant with (endless) loop in ide_do_request?

And where do_request() callers obtain channel lock so that do_request()
can release and reacquire it?

My problem is that fsck reliable dies between 79.6 and 81% of its
run - on UP machine with SMP kernel:

NMI detected lockup on CPU0 ...

Stack trace: do_request + 315/924
do_ide_request
generic_unplug_device
blk_run_queues
do_page_cache_readahead
page_cache_readahead
do_generic_file_read
generic_file_read
file_read_actor
vfs_read
sys_read

do_request+315 is clear_bit(IDE_BUSY, channel->active) at line 606.

The do_ide_request()'s loop

while (!test_and_set_bit(IDE_BUSY, ch->active)) {
do_request(ch)
}

looks very suspicious to me - it will loop here until the end of world,
as there is nothing in queue, so do_request() will always exit
with IDE_BUSY cleared.

Next question is: with this stack trace, where you obtained ch->lock,
so that do_request() can do call to spin_unlock(ch->lock) ? It looks
to me like that I should get 'unlocking unlocked spinlock' with
appropriate debug.

What (probably) happened is that hardware finished request before
spin_lock_irq(ch->lock) (at line 749) was executed, we quit with
IDE_BUSY cleared, and it was last thing we did... Maybe I should
go back to IDE-98?
Thanks,
Petr Vandrovec
vandrove@vc.cvut.cz

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