On 3/27/24 16:37, Jens Axboe wrote:
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.
Right, to my knowledge release does nothing for write; read;
ordering, and all ops after can leak before the barrier.
--
Pavel Begunkov
