diff --git a/io_uring/io_uring.h b/io_uring/io_uring.h index 9d70b2cf7b1e..913dbcebe5c9 100644 --- a/io_uring/io_uring.h +++ b/io_uring/io_uring.h @@ -284,7 +284,14 @@ static inline bool io_sqring_full(struct io_ring_ctx *ctx) { struct io_rings *r = ctx->rings; - return READ_ONCE(r->sq.tail) - ctx->cached_sq_head == ctx->sq_entries; + /* + * SQPOLL must use the actual sqring head, as using the cached_sq_head + * is race prone if the SQPOLL thread has grabbed entries but not yet + * committed them to the ring. For !SQPOLL, this doesn't matter, but + * since this helper is just used for SQPOLL sqring waits (or POLLOUT), + * just read the actual sqring head unconditionally. + */ + return READ_ONCE(r->sq.tail) - READ_ONCE(r->sq.head) == ctx->sq_entries; } static inline unsigned int io_sqring_entries(struct io_ring_ctx *ctx)