On 3/27/24 9:45 AM, Jens Axboe wrote: >> smp_mb(), see the comment below, and fwiw "_after_atomic" would not >> work. > > For this one, I think all we need to do is have the wq_list_empty() > check be fully stable. If we read: > > nr_wait = atomic_read(&ctx->cq_wait_nr); > > right before a waiter does: > > atomic_set(&ctx->cq_wait_nr, foo); > set_current_state(TASK_INTERRUPTIBLE); > > then we need to ensure that the "I have work" check in > io_cqring_wait_schedule() sees the work. The spin_unlock() has release > semantics, and the current READ_ONCE() for work check sbould be enough, > no? To answer my own question - no, it's not enough. Let me think about this a bit. -- Jens Axboe
