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io_uring_poll: kill the no longer necessary barrier after poll_wait()

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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 <oleg@redhat.com>
Link: https://lore.kernel.org/r/20250107162730.GA18940@redhat.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Oleg Nesterov 2025-01-07 17:27:30 +01:00 committed by Christian Brauner
parent 10b02a2cfe
commit 4e15fa8305
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GPG Key ID: 91C61BC06578DCA2
1 changed files with 4 additions and 5 deletions
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9
io_uring/io_uring.c
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@ -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;