On Mon, Oct 30 2006, Arjan van de Ven wrote:
>
> > which has always been considered safe, while not very pretty.
>
>
> actually it's different I think (based on a brief inspection of the
> code, I could well be wrong):
> get_request_wait() causes a get_request() call with a GFP_NOIO gfp_mask
> which perculates upto cfq_set_request() as argument.
> cfq_set_request() then calls the inline cfq_get_queue() (which isn't in
> the backtrace due to inlining) which does
> } else if (gfp_mask & __GFP_WAIT) {
> /*
> * Inform the allocator of the fact that we will
> * just repeat this allocation if it fails, to allow
> * the allocator to do whatever it needs to attempt to
> * free memory.
> */
> spin_unlock_irq(cfqd->queue->queue_lock);
>
> which enables interrupts right smack in the middle of holding a whole
> bunch of locks.....
Where do you get 'a bunch' from? If you call get_request() with a
gfp_mask that includes __GFP_WAIT with a spinlock held, it's a bug. Just
as if you had called kmalloc() or similar with __GFP_WAIT set and
holding a lock. cfq even includes a warning check:
might_sleep_if(gfp_mask & __GFP_WAIT);
So there's no bug there, cfq even grabbed the lock on its own before
calling cfq_get_queue().
> so to me it looks like lockdep at least has the appearance of moaning
> about a reasonably fishy situation...
To me it looks more about lockdep complaining because it doesn't grok
the full picture. The question is how to shut it up.
--
Jens Axboe
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
