On Mon, December 17, 2007 2:06 pm, Jens Axboe wrote: > On Sun, Dec 16 2007, Adrian McMenamin wrote: > > Few notes: Thanks for these, very helpful. > > - Compare rq_data_dir() with WRITE, don't just assume that any non-zero > will be a write. > > - You need to offload this request handling to a workqueue of some sort, > your current request handling is very broken for two reasons: One is > that interrupts are still disabled when you drop your queue lock, so > you cannot use sleeping functions like GFP_KERNEL allocations or > wait_event(). The other is that it's illegal to sleep from your > request_fn context in the first place, since you could be stalling > others. Ah. OK. Funnily enough an earlier version did offload to a workqueue but i thought that was too convoluted. I didn't realise interrupts were disabled inside the request_fn context. > > - You also seem to be busy waiting for other transactions to finish. Any > idea how long those might take? Perhaps put an upper bound on this > waiting, and/or do blocking waits? > Well, when the register bit clears they are over, seems to be about 200 - 400 microseconds or there abouts (ie that length of time between the interrupt signalling that the transfer is over and the bit clearing to allow a new transfer) - so I could time that out at say HZ/2 and be very safe. > - I'm assuming this hardware can't do sg transfers? > Afraid not. - To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
