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authorXiaoguang Wang <xiaoguang.wang@linux.alibaba.com>2020-05-20 15:35:03 +0800
committerJens Axboe <axboe@kernel.dk>2020-05-20 08:41:26 -0600
commit6b668c9b7fc6fc0c313cdaee8b75d17f4d954ab5 (patch)
tree2e3467201427f4f9fd45ceab17077f3aa5fafa10
parent310672552f4aea2ad50704711aa3cdd45f5441e9 (diff)
io_uring: don't submit sqes when ctx->refs is dying
When IORING_SETUP_SQPOLL is enabled, io_ring_ctx_wait_and_kill() will wait for sq thread to idle by busy loop: while (ctx->sqo_thread && !wq_has_sleeper(&ctx->sqo_wait)) cond_resched(); Above loop isn't very CPU friendly, it may introduce a short cpu burst on the current cpu. If ctx->refs is dying, we forbid sq_thread from submitting any further SQEs. Instead they just get discarded when we exit. Signed-off-by: Xiaoguang Wang <xiaoguang.wang@linux.alibaba.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
-rw-r--r--fs/io_uring.c13
1 files changed, 2 insertions, 11 deletions
diff --git a/fs/io_uring.c b/fs/io_uring.c
index 50f079417911..0b51f21e5432 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6175,7 +6175,8 @@ static int io_sq_thread(void *data)
}
mutex_lock(&ctx->uring_lock);
- ret = io_submit_sqes(ctx, to_submit, NULL, -1);
+ if (likely(!percpu_ref_is_dying(&ctx->refs)))
+ ret = io_submit_sqes(ctx, to_submit, NULL, -1);
mutex_unlock(&ctx->uring_lock);
timeout = jiffies + ctx->sq_thread_idle;
}
@@ -7465,16 +7466,6 @@ static void io_ring_ctx_wait_and_kill(struct io_ring_ctx *ctx)
percpu_ref_kill(&ctx->refs);
mutex_unlock(&ctx->uring_lock);
- /*
- * Wait for sq thread to idle, if we have one. It won't spin on new
- * work after we've killed the ctx ref above. This is important to do
- * before we cancel existing commands, as the thread could otherwise
- * be queueing new work post that. If that's work we need to cancel,
- * it could cause shutdown to hang.
- */
- while (ctx->sqo_thread && !wq_has_sleeper(&ctx->sqo_wait))
- cond_resched();
-
io_kill_timeouts(ctx);
io_poll_remove_all(ctx);