From: "Christian König" <ckoenig.leichtzumerken@gmail.com> To: "Sergey Senozhatsky" <senozhatsky@chromium.org>, "Christian König" <christian.koenig@amd.com> Cc: Sumit Semwal <sumit.semwal@linaro.org>, Gustavo Padovan <gustavo@padovan.org>, Tomasz Figa <tfiga@chromium.org>, Ricardo Ribalda <ribalda@chromium.org>, Christoph Hellwig <hch@infradead.org>, linux-media@vger.kernel.org, dri-devel@lists.freedesktop.org, linaro-mm-sig@lists.linaro.org, linux-kernel@vger.kernel.org Subject: Re: [Linaro-mm-sig] Re: [PATCH] dma-fence: allow dma fence to have their own lock Date: Wed, 1 Jun 2022 14:45:42 +0200 [thread overview] Message-ID: <33aba213-b6ad-4a15-9272-c62f5dfb1fb7@gmail.com> (raw) In-Reply-To: <YpWCvniLzJfcp684@google.com> Am 31.05.22 um 04:51 schrieb Sergey Senozhatsky: > On (22/05/30 16:55), Christian König wrote: >> Am 30.05.22 um 16:22 schrieb Sergey Senozhatsky: >>> [SNIP] >>> So the `lock` should have at least same lifespan as the DMA fence >>> that borrows it, which is impossible to guarantee in our case. >> Nope, that's not correct. The lock should have at least same lifespan as the >> context of the DMA fence. > How does one know when it's safe to release the context? DMA fence > objects are still transparently refcount-ed and "live their own lives", > how does one synchronize lifespans? Well, you don't. If you have a dynamic context structure you need to reference count that as well. In other words every time you create a fence in your context you need to increment the reference count and every time a fence is release you decrement it. If you have a static context structure like most drivers have then you must make sure that all fences at least signal before you unload your driver. We still somewhat have a race when you try to unload a driver and the fence_ops structure suddenly disappear, but we currently live with that. Apart from that you are right, fences can live forever and we need to deal with that. Regards, Christian. > _______________________________________________ > Linaro-mm-sig mailing list -- linaro-mm-sig@lists.linaro.org > To unsubscribe send an email to linaro-mm-sig-leave@lists.linaro.org
WARNING: multiple messages have this Message-ID (diff)
From: "Christian König" <ckoenig.leichtzumerken@gmail.com> To: "Sergey Senozhatsky" <senozhatsky@chromium.org>, "Christian König" <christian.koenig@amd.com> Cc: linaro-mm-sig@lists.linaro.org, Gustavo Padovan <gustavo@padovan.org>, linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org, Tomasz Figa <tfiga@chromium.org>, Christoph Hellwig <hch@infradead.org>, Ricardo Ribalda <ribalda@chromium.org>, Sumit Semwal <sumit.semwal@linaro.org>, linux-media@vger.kernel.org Subject: Re: [Linaro-mm-sig] Re: [PATCH] dma-fence: allow dma fence to have their own lock Date: Wed, 1 Jun 2022 14:45:42 +0200 [thread overview] Message-ID: <33aba213-b6ad-4a15-9272-c62f5dfb1fb7@gmail.com> (raw) In-Reply-To: <YpWCvniLzJfcp684@google.com> Am 31.05.22 um 04:51 schrieb Sergey Senozhatsky: > On (22/05/30 16:55), Christian König wrote: >> Am 30.05.22 um 16:22 schrieb Sergey Senozhatsky: >>> [SNIP] >>> So the `lock` should have at least same lifespan as the DMA fence >>> that borrows it, which is impossible to guarantee in our case. >> Nope, that's not correct. The lock should have at least same lifespan as the >> context of the DMA fence. > How does one know when it's safe to release the context? DMA fence > objects are still transparently refcount-ed and "live their own lives", > how does one synchronize lifespans? Well, you don't. If you have a dynamic context structure you need to reference count that as well. In other words every time you create a fence in your context you need to increment the reference count and every time a fence is release you decrement it. If you have a static context structure like most drivers have then you must make sure that all fences at least signal before you unload your driver. We still somewhat have a race when you try to unload a driver and the fence_ops structure suddenly disappear, but we currently live with that. Apart from that you are right, fences can live forever and we need to deal with that. Regards, Christian. > _______________________________________________ > Linaro-mm-sig mailing list -- linaro-mm-sig@lists.linaro.org > To unsubscribe send an email to linaro-mm-sig-leave@lists.linaro.org
next prev parent reply other threads:[~2022-06-01 12:45 UTC|newest] Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-05-30 14:22 [PATCH] dma-fence: allow dma fence to have their own lock Sergey Senozhatsky 2022-05-30 14:22 ` Sergey Senozhatsky 2022-05-30 14:55 ` Christian König 2022-05-30 14:55 ` Christian König 2022-05-30 15:09 ` Sergey Senozhatsky 2022-05-30 15:09 ` Sergey Senozhatsky 2022-05-30 15:45 ` Sergey Senozhatsky 2022-05-30 15:45 ` Sergey Senozhatsky 2022-06-01 13:50 ` [Linaro-mm-sig] " Christian König 2022-06-01 13:50 ` Christian König 2022-05-31 2:51 ` Sergey Senozhatsky 2022-05-31 2:51 ` Sergey Senozhatsky 2022-06-01 12:45 ` Christian König [this message] 2022-06-01 12:45 ` [Linaro-mm-sig] " Christian König 2022-06-01 13:22 ` Daniel Vetter 2022-06-01 13:22 ` Daniel Vetter 2022-06-01 13:52 ` Christian König 2022-06-01 14:27 ` Sergey Senozhatsky 2022-06-01 14:27 ` Sergey Senozhatsky 2022-06-01 14:38 ` Christian König 2022-06-01 14:38 ` Christian König 2022-06-01 14:52 ` Sergey Senozhatsky 2022-06-01 14:52 ` Sergey Senozhatsky 2022-06-01 15:06 ` Christian König 2022-06-01 15:06 ` Christian König
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