On 8/24/22 17:08, Christian König wrote: > Am 24.08.22 um 12:22 schrieb Dmitry Osipenko: >> Move dma-buf attachment API functions to the dynamic locking >> specification. >> The strict locking convention prevents deadlock situations for dma-buf >> importers and exporters. >> >> Previously, the "unlocked" versions of the attachment API functions >> weren't taking the reservation lock and this patch makes them to take >> the lock. > > Didn't we concluded that we need to keep the attach and detach callbacks > without the lock and only move the map/unmap callbacks over? > > Otherwise it won't be possible for drivers to lock multiple buffers if > they have to shuffle things around for a specific attachment. We did conclude that. The attach/detach dma-buf ops are unlocked, but the map_dma_buf/unmap_dma_buf must be invoked under lock and dma_buf_dynamic_attach_unlocked() maps dma-buf if either importer or exporter can't handle the dynamic mapping [1]. [1] https://elixir.bootlin.com/linux/v6.0-rc2/source/drivers/dma-buf/dma-buf.c#L869 Hence I re-arranged the dma_resv_lock() in dma_buf_dynamic_attach_unlocked() to move both pinning and mapping under the held lock. -- Best regards, Dmitry
