Messages in this thread |  | | Date | Tue, 4 Sep 2001 19:17:59 +0200 | From | Jens Axboe <> | Subject | Re: io_request_lock/queue_lock patch |
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On Tue, Sep 04 2001, Jonathan Lahr wrote: > > > 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.
You fixed SCSI for q->queue_head usage, that part looks ok. The low level call backs are a much bigger mess though. And you broke IDE, cciss, cpqarray, DAC960, etc etc in the process.
> 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 can certainly understand that, but I really hope you see what I mean that we cannot change this locking now.
-- Jens Axboe
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