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 codes are not friendly, indeed I think this busy loop will introduce a
cpu burst in current cpu, though it maybe short.
In this patch, if ctx->refs is dying, we forbids sq_thread from submitting
sqes anymore, just discard leftover sqes.
Signed-off-by: Xiaoguang Wang <xiaoguang.wang@xxxxxxxxxxxxxxxxx>
---
fs/io_uring.c | 13 ++-----------
1 file changed, 2 insertions(+), 11 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index f9f79ac5ac7b..ed0c22eb9808 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -6040,7 +6040,8 @@ static int io_sq_thread(void *data)
}
mutex_lock(&ctx->uring_lock);
- ret = io_submit_sqes(ctx, to_submit, NULL, -1, true);
+ if (likely(!percpu_ref_is_dying(&ctx->refs)))
+ ret = io_submit_sqes(ctx, to_submit, NULL, -1, true);
mutex_unlock(&ctx->uring_lock);
timeout = jiffies + ctx->sq_thread_idle;
}
@@ -7311,16 +7312,6 @@ 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);
--
2.17.2
