On 7/23/07, Jens Axboe <[email protected]> wrote:
On Sun, Jul 22 2007, Satyam Sharma wrote:
> Hi Walter,
>
> Thanks for reporting this.
>
> On 7/22/07, walter harms <[email protected]> wrote:
>> hello all,
>> on my asus notebook tm620 there is a crash with 2.6.22 and 2.6.21
>
> Did this happen when you were resuming from a suspend-to-ram/disk?
> [ I ask because I see swsusp in the trace below, linux-pm added to Cc: ]
>
>> ....
>> Using IPI Shortcut mode
>> WARNING: at block/ll_rw_blk.c:1575 blk_remove_plug()
>> [<c01ac87e>] blk_remove_plug+0x36/0x5a
>> [<c01ac8b6>] __generic_unplug_device+0x14/0x1f
>> [<c01ad587>] __make_request+0x39b/0x49c
>> [<c01abc8c>] generic_make_request+0x228/0x255
>> [<c01adb54>] submit_bio+0xa5/0xac
>> [<c013e233>] mempool_alloc+0x37/0xae
>> [<c01314dc>] submit+0xc2/0x11d
>> [<c0131585>] bio_read_page+0x24/0x27
>> [<c013188b>] swsusp_check+0x4f/0xaf
>> [<c012f6c2>] software_resume+0x5f/0x108
>> [<c037867e>] kernel_init+0xb0/0x212
>> [<c0103a16>] ret_from_fork+0x6/0x1c
>> [<c03785ce>] kernel_init+0x0/0x212
>> [<c03785ce>] kernel_init+0x0/0x212
>> [<c010465b>] kernel_thread_helper+0x7/0x10
>> =======================
>
> Surprising, that's a WARN_ON(!irqs_disabled()) but IRQs are disabled
> alright on that codepath. OTOH, __make_request() is heavily goto-driven,
> uses the non-save/restore variants of spin_lock_irq, and does not even
> balance locks / unlocks for some error paths ... gaah.
__make_request() must be called from process context, hence
spin_lock_irq() is perfectly already and the fastest way to go. And of
course the locking is balanced! So please save your 'gaah's for code
you actually took the time to try and understand.
You're right, I didn't really look at that code for long (it even explicitly
comments about what's going with the locking in there!) sorry about
that.
[ Off-topic: BTW does every call to __make_request() end up in
blk_remove_plug()? Since you're explicitly making the assumption
that it *must* be called from process context (and hence the use of
the non-save/restore variants), you could consider putting a
WARN_ON(irqs_disabled()) over there, and perhaps a WARN_ON
(!spin_is_locked(queue_lock)) in blk_remove_plug() instead, and
other such similar functions that currently have the !irqs_disabled
check. This way you'd effectively cover _both_ the assertions,
and in appropriate places -- just a suggestion. ]
But it does look like unbalanced irq disable/enable calls. I'd guess in
the suspend/resume path. Obviously something more esoteric, since this
is the first such report for 2.6.22, so like some not-very-used driver
for instance.
Now that I do look at the codepath, it does seem surprising irqs were
not disabled there. There are a bunch of calls to _other_ functions
between the spin_lock_irq and the blk_remove_plug via
__generic_unplug_device that would also have complained about
!irqs_disabled.
Walter, does this happen reproducibly?
Satyam
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