Hi, On 6/21/23 20:21, T.J. Mercier wrote: > On Mon, May 29, 2023 at 3:46 PM Dmitry Osipenko > <dmitry.osipenko@xxxxxxxxxxxxx> wrote: >> >> Don't assert held dma-buf reservation lock on memory mapping of exported >> buffer. >> >> We're going to change dma-buf mmap() locking policy such that exporters >> will have to handle the lock. The previous locking policy caused deadlock >> problem for DRM drivers in a case of self-imported dma-bufs once these >> drivers are moved to use reservation lock universally. The problem >> solved by moving the lock down to exporters. This patch prepares dma-buf >> heaps for the locking policy update. >> > Hi Dmitry, > > I see that in patch 6 of this series calls to > dma_resv_lock/dma_resv_unlock have been added to the > drm_gem_shmem_helper functions and some exporters. But I'm curious why > no dma_resv_lock/dma_resv_unlock calls were added to these two dma-buf > heap exporters for mmap? DMA-buf heaps are exporters, drm_gem_shmem_helper is importer. Locking rules are different for importers and exporters. DMA-heaps use own locking, they can be moved to resv lock in the future. DMA-heaps don't protect internal data in theirs mmap() implementations, nothing to protect there. -- Best regards, Dmitry
