On Thu, Mar 09, 2023 at 08:48:08AM -0500, Stefan Hajnoczi wrote: > Hi, > For block I/O an application can queue excess SQEs in userspace when the > SQ ring becomes full. For network and IPC operations that is not > possible because deadlocks can occur when socket, pipe, and eventfd SQEs > cannot be submitted. Can you explain a bit the deadlock in case of network application? io_uring does support to queue many network SQEs via IOSQE_IO_LINK, at least for send. > > Sometimes the application does not know how many SQEs/CQEs are needed upfront > and that's when we face this challenge. When running out of SQEs, the application can call io_uring_enter() to submit queued SQEs immediately without waiting for get events, then once io_uring_enter() returns, you get free SQEs for moving one. > > A simple solution is to call io_uring_setup(2) with a higher entries > value than you'll ever need. However, if that value is exceeded then > we're back to the deadlock scenario and that worries me. Can you please explain the deadlock scenario? Thanks, Ming
