From: Oleg Nesterov Date: Tue, 7 Jan 2025 16:27:30 +0000 (+0100) Subject: io_uring_poll: kill the no longer necessary barrier after poll_wait() X-Git-Tag: v6.13-rc7~23^2^2^2~2 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=4e15fa8305deecdf20233558ed9f7a8a62b708fd;p=thirdparty%2Flinux.git io_uring_poll: kill the no longer necessary barrier after poll_wait() Now that poll_wait() provides a full barrier we can remove smp_rmb() from io_uring_poll(). In fact I don't think smp_rmb() was correct, it can't serialize LOADs and STOREs. Signed-off-by: Oleg Nesterov Link: https://lore.kernel.org/r/20250107162730.GA18940@redhat.com Signed-off-by: Christian Brauner --- diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index 06ff41484e29c..a64a82b93b865 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -2809,13 +2809,12 @@ static __poll_t io_uring_poll(struct file *file, poll_table *wait) if (unlikely(!ctx->poll_activated)) io_activate_pollwq(ctx); - - poll_wait(file, &ctx->poll_wq, wait); /* - * synchronizes with barrier from wq_has_sleeper call in - * io_commit_cqring + * provides mb() which pairs with barrier from wq_has_sleeper + * call in io_commit_cqring */ - smp_rmb(); + poll_wait(file, &ctx->poll_wq, wait); + if (!io_sqring_full(ctx)) mask |= EPOLLOUT | EPOLLWRNORM;