Messages in this thread | | | Date | Mon, 30 Oct 2006 09:26:48 +0100 | From | Jens Axboe <> | Subject | Re: [PATCH 06/11] uml ubd driver: ubd_io_lock usage fixup |
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On Sun, Oct 29 2006, Blaisorblade wrote: > Add some comments about requirements for ubd_io_lock and expand its use. > > When an irq signals that the "controller" (i.e. another thread on the host, > which does the actual requests and is the only one blocked on I/O on the > host) has done some work, we call again the request function ourselves > (do_ubd_request). > > We now do that with ubd_io_lock held - that's useful to protect against > concurrent calls to elv_next_request and so on.
Not only useful, required, as I think I complained about a year or more ago :-)
> XXX: Maybe we shouldn't call at all the request function. Input needed on > this. Are we supposed to plug and unplug the queue? That code "indirectly" > does that by setting a flag, called do_ubd, which makes the request function > return (it's a residual of 2.4 block layer interface).
Sometimes you need to. I'd probably just remove the do_ubd check and always recall the request function when handling completions, it's easier and safe.
-- Jens Axboe
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