Sure, I will send a new patch using completion instead of dma-fence Thanks, Ofir
-----Original Message----- From: Greg Kroah-Hartman <[email protected]> Sent: Tuesday, July 14, 2020 09:37 To: Daniel Vetter <[email protected]> Cc: Jason Gunthorpe <[email protected]>; Oded Gabbay <[email protected]>; Linux Kernel Mailing List <[email protected]>; SW_Drivers <[email protected]>; Ofir Bitton <[email protected]> Subject: Re: [PATCH 1/3] habanalabs: implement dma-fence mechanism On Mon, Jul 13, 2020 at 09:08:55PM +0200, Daniel Vetter wrote: > On Mon, Jul 13, 2020 at 9:03 PM Jason Gunthorpe <[email protected]> wrote: > > > > On Mon, Jul 13, 2020 at 08:34:12PM +0200, Daniel Vetter wrote: > > > On Mon, Jul 13, 2020 at 5:57 PM Greg Kroah-Hartman > > > <[email protected]> wrote: > > > > > > > > On Mon, Jul 13, 2020 at 06:54:22PM +0300, Oded Gabbay wrote: > > > > > From: Ofir Bitton <[email protected]> > > > > > > > > > > Instead of using standard dma-fence mechanism designed for > > > > > GPU's, we introduce our own implementation based on the former > > > > > one. This implementation is much more sparse than the > > > > > original, contains only mandatory functionality required by the > > > > > driver. > > > > > > > > Sad you can't use the in-kernel code for this, I really don't > > > > understand what's wrong with using it as-is. > > > > > > > > Daniel, why do we need/want duplicate code floating around in > > > > the tree like this? > > > > > > The rules around dma-fence are ridiculously strict, and it only > > > makes sense to inflict that upon you if you actually want to > > > participate in the cross driver uapi built up around dma-buf and > > > dma-fence. > > > > > > I've recently started some lockdep annotations to better enforce > > > these rules (and document them), and it's finding tons of subtle > > > bugs even in drivers/gpu (and I only just started with annotating drivers: > > > > > > https://lore.kernel.org/dri-devel/20200707201229.472834-1-daniel.v > > > [email protected]/ > > > > > > You really don't want to deal with this if you don't have to. If > > > drivers/gpu folks (who created this) aren't good enough to > > > understand it, maybe it's not a good idea to sprinkle this all > > > over the tree. And fundamentally all this is is a slightly fancier > > > struct completion. Use that one instead, or a wait_queue. > > > > > > I discussed this a bit with Oded, and he thinks it's easier to > > > copypaste and simplify, but given that all other drivers seem to > > > get by perfectly well with completion or wait_queue, I'm not sure > > > that's a solid case. > > > > > > Also adding Jason Gunthorpe, who very much suggested this should > > > be limited to dma-buf/gpu related usage only. > > > > Without all the cross-driver stuff dma_fence is just a completion. > > Using dma_fence to get a completion is big abuse of what it is > > intended for. > > > > I think the only problem with this patch is that it keeps too much > > of the dma_fence stuff around. From what I could tell it really just > > wants to add a kref and completion to struct hl_cs_compl and delete > > everything to do with dma_fence. > > Yeah, that's what I recommended doing too. error flag might be needed > too I think, but that's it. Ok, so this should be made much simpler and not use this copy/paste code at all. I can accept that :) Ofir, care to redo this? thanks, greg k-h
