Is it safe to submit and reap IOs in different threads?

["Bhatia, Sumeet" <sumee@amazon.com>]

Hello,

My application has a thread per disk (aka producer_thread) that generates disk operations. I have io-uring context per disk to ensure iouring submissions are from a single thread.

producer_thread executes only if new disk operations are to be submitted else it yields. It'll be significant code change to modify this behavior. For this reason I spin up a new thread (aka consumer thread) per io-uring context to reap IO completions.

My reading of fs/io_uring.c suggests it is safe to submit IOs from producer_thread and reap IOs from consumer_thread. My prototype based on liburing (Ref: https://pastebin.com/6u2FZB0D) works fine too. 

I would like to get your thoughts on whether this approach is indeed safe or am I overlooking any race condition?

Thanks,
Sumeet