Re: [PATCH] io_uring: remove WRITE_ONCE() in io_uring_create()

[Caleb Sander Mateos <csander@purestorage.com>]

On Tue, Sep 2, 2025 at 6:20 PM Jens Axboe <axboe@kernel.dk> wrote:
>
> On 9/2/25 3:51 PM, Caleb Sander Mateos wrote:
> > There's no need to use WRITE_ONCE() to set ctx->submitter_task in
> > io_uring_create() since no other thread can access the io_ring_ctx until
> > a file descriptor is associated with it. So use a normal assignment
> > instead of WRITE_ONCE().
>
> Would probably warrant a code comment to that effect, as just reading
> the code would be slightly confusing after this.

Could you elaborate on why you find it confusing? I wouldn't expect to
see WRITE_ONCE() or any other atomic operation used when initializing
memory prior to it being made accessible from other threads. It looks
like commit 8579538c89e3 ("io_uring/msg_ring: fix remote queue to
disabled ring") added the WRITE_ONCE() both here and in
io_register_enable_rings(). But it's only needed in
io_register_enable_rings(), where the io_ring_ctx already has an
associated file descriptor and may be accessed concurrently from
multiple threads.

Thanks,
Caleb