> You are now browsing the request list without agreeing on what lock is
> being held -- what happens to drivers assuming that io_request_lock
> protects the list? Boom. For 2.4 we simply cannot afford to muck around
> with this, it's jsut too dangerous. For 2.5 I already completely removed
> the io_request_lock (also helps to catch references to it from drivers).
In this patch, io_request_lock and queue_lock are both acquired in
generic_unplug_device, so request_fn invocations protect request queue
integrity. __make_request acquires queue_lock instead of io_request_lock
thus protecting queue integrity while allowing greater concurrency.
Nevertheless, I understand your unwillingness to change locking as
pervasive as io_request_lock. Such changes would of course involve
risk. I am simply trying to improve 2.4 i/o performance, since 2.4
could have a long time left to live.
> I agree with your SCSI approach, it's the same we took. Low level
> drivers must be responsible for their own locking, the mid layer should
> not pre-grab anything for them.
Yes, calling out of subsystem scope with locks held can cause problems.
Thanks for your feedback.
Jonathan
-- Jonathan Lahr IBM Linux Technology Center Beaverton, Oregon lahr@us.ibm.com 503-578-3385- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Fri Sep 07 2001 - 21:00:26 EST