BACKPORT: ANDROID: dma-buf: heaps: replace mutex lock with spinlock
We should use spinlock to protect page pool's critical section as 1. The critical section is short, using spinlock is more efficient. 2. Spinlock could protect priority inversion. Ex. Low priority thread (dmabuf-deferred) hold the page lock but get scheduled out under heavy loading. Then the other high priority threads need to wait for dmabuf-deferred to release the lock. It causes long allocation latency and possible UI jank. Also, we could move NR_KERNEL_MISC_RECLAIMABLE stat out of the critical section to make it shorter as mod_node_page_state can handle concurrent access cases. Conflicts: drivers/dma-buf/heaps/page_pool.h drivers/dma-buf/heaps/page_pool.c 1. The android13-5.15 KMI is frozen, and the modification to struct dmabuf_page_pool in the original patch would break the KMI. Instead we wrap dmabuf_page_pool allocations in a struct dmabuf_page_pool_with_spinlock which also contains a spinlock replacement for dmabuf_page_pool's mutex. No callers should attempt to acquire dmabuf_page_pool's mutex on this branch, so it is locked immediately after initialization and never unlocked. (cherry picked from commit 060e38dc) Bug: 245454030 Change-Id: I15f349f9e893621f71ca79f1de037de184c33edf Signed-off-by:T.J. Mercier <tjmercier@google.com>
Loading