On Thu, 2024-05-23 at 15:46 +0800, Heng Qi wrote: > This reverts commit 4d4ac2ececd3c42a08dd32a6e3a4aaf25f7efe44. > > When the following snippet is run, lockdep will report a deadlock[1]. > > /* Acquire all queues dim_locks */ > for (i = 0; i < vi->max_queue_pairs; i++) > mutex_lock(&vi->rq[i].dim_lock); > > There's no deadlock here because the vq locks are always taken > in the same order, but lockdep can not figure it out, and we > can not make each lock a separate class because there can be more > than MAX_LOCKDEP_SUBCLASSES of vqs. > > However, dropping the lock is harmless: > 1. If dim is enabled, modifications made by dim worker to coalescing > params may cause the user's query results to be dirty data. It looks like the above can confuse the user-space/admin? Have you considered instead re-factoring virtnet_send_rx_notf_coal_cmds() to avoid acquiring all the mutex in sequence? Thanks! Paolo
