From: Stefan Bühler Date: Wed, 24 Apr 2019 21:54:17 +0000 (+0200) Subject: io_uring: remove unnecessary barrier before wq_has_sleeper X-Git-Url: http://git.cdn.openwrt.org/?a=commitdiff_plain;h=4f7067c3fb7f2974363a28c597a41949d971af02;p=openwrt%2Fstaging%2Fblogic.git io_uring: remove unnecessary barrier before wq_has_sleeper wq_has_sleeper has a full barrier internally. The smp_rmb barrier in io_uring_poll synchronizes with it. Signed-off-by: Stefan Bühler Signed-off-by: Jens Axboe --- diff --git a/fs/io_uring.c b/fs/io_uring.c index 7ab93e854eb2..bb71b7f00bb3 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -418,12 +418,6 @@ static void io_commit_cqring(struct io_ring_ctx *ctx) /* order cqe stores with ring update */ smp_store_release(&ring->r.tail, ctx->cached_cq_tail); - /* - * Write sider barrier of tail update, app has read side. See - * comment at the top of this file. - */ - smp_wmb(); - if (wq_has_sleeper(&ctx->cq_wait)) { wake_up_interruptible(&ctx->cq_wait); kill_fasync(&ctx->cq_fasync, SIGIO, POLL_IN); @@ -2677,7 +2671,10 @@ static __poll_t io_uring_poll(struct file *file, poll_table *wait) __poll_t mask = 0; poll_wait(file, &ctx->cq_wait, wait); - /* See comment at the top of this file */ + /* + * synchronizes with barrier from wq_has_sleeper call in + * io_commit_cqring + */ smp_rmb(); if (READ_ONCE(ctx->sq_ring->r.tail) - ctx->cached_sq_head != ctx->sq_ring->ring_entries)