io_wq_put_and_exit() is called from do_exit(), but all requests in io_wq aren't cancelled in io_uring_cancel_generic() called from do_exit(). Meantime io_wq IO code path may share resource with normal iopoll code path. So if any HIPRI request is pending in io_wq_submit_work(), this request may not get resouce for moving on, given iopoll isn't possible in io_wq_put_and_exit(). The issue can be triggered when terminating 't/io_uring -n4 /dev/nullb0' with default null_blk parameters. Fix it by always cancelling all requests in io_wq from io_uring_cancel_generic(), and this way is reasonable because io_wq destroying follows cancelling requests immediately. Based on one patch from Chengming. Closes: https://lore.kernel.org/linux-block/3893581.1691785261@xxxxxxxxxxxxxxxxxxxxxx/ Reported-by: David Howells <dhowells@xxxxxxxxxx> Cc: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>, Signed-off-by: Ming Lei <ming.lei@xxxxxxxxxx> --- io_uring/io_uring.c | 40 ++++++++++++++++++++++++++++------------ 1 file changed, 28 insertions(+), 12 deletions(-) diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c index e7675355048d..18d5ab969c29 100644 --- a/io_uring/io_uring.c +++ b/io_uring/io_uring.c @@ -144,7 +144,7 @@ struct io_defer_entry { static bool io_uring_try_cancel_requests(struct io_ring_ctx *ctx, struct task_struct *task, - bool cancel_all); + bool cancel_all, bool *wq_cancelled); static void io_queue_sqe(struct io_kiocb *req); @@ -3049,7 +3049,7 @@ static __cold void io_ring_exit_work(struct work_struct *work) if (ctx->flags & IORING_SETUP_DEFER_TASKRUN) io_move_task_work_from_local(ctx); - while (io_uring_try_cancel_requests(ctx, NULL, true)) + while (io_uring_try_cancel_requests(ctx, NULL, true, NULL)) cond_resched(); if (ctx->sq_data) { @@ -3231,12 +3231,13 @@ static __cold bool io_uring_try_cancel_iowq(struct io_ring_ctx *ctx) static __cold bool io_uring_try_cancel_requests(struct io_ring_ctx *ctx, struct task_struct *task, - bool cancel_all) + bool cancel_all, bool *wq_cancelled) { - struct io_task_cancel cancel = { .task = task, .all = cancel_all, }; + struct io_task_cancel cancel = { .task = task, .all = true, }; struct io_uring_task *tctx = task ? task->io_uring : NULL; enum io_wq_cancel cret; bool ret = false; + bool wq_active = false; /* set it so io_req_local_work_add() would wake us up */ if (ctx->flags & IORING_SETUP_DEFER_TASKRUN) { @@ -3249,7 +3250,7 @@ static __cold bool io_uring_try_cancel_requests(struct io_ring_ctx *ctx, return false; if (!task) { - ret |= io_uring_try_cancel_iowq(ctx); + wq_active = io_uring_try_cancel_iowq(ctx); } else if (tctx && tctx->io_wq) { /* * Cancels requests of all rings, not only @ctx, but @@ -3257,11 +3258,20 @@ static __cold bool io_uring_try_cancel_requests(struct io_ring_ctx *ctx, */ cret = io_wq_cancel_cb(tctx->io_wq, io_cancel_task_cb, &cancel, true); - ret |= (cret != IO_WQ_CANCEL_NOTFOUND); + wq_active = (cret != IO_WQ_CANCEL_NOTFOUND); } + ret |= wq_active; + if (wq_cancelled) + *wq_cancelled = !wq_active; - /* SQPOLL thread does its own polling */ - if ((!(ctx->flags & IORING_SETUP_SQPOLL) && cancel_all) || + /* + * SQPOLL thread does its own polling + * + * io_wq may share IO resources(such as requests) with iopoll, so + * iopoll requests have to be reapped for providing forward + * progress to io_wq cancelling + */ + if (!(ctx->flags & IORING_SETUP_SQPOLL) || (ctx->sq_data && ctx->sq_data->thread == current)) { while (!wq_list_empty(&ctx->iopoll_list)) { io_iopoll_try_reap_events(ctx); @@ -3313,11 +3323,12 @@ __cold void io_uring_cancel_generic(bool cancel_all, struct io_sq_data *sqd) atomic_inc(&tctx->in_cancel); do { bool loop = false; + bool wq_cancelled; io_uring_drop_tctx_refs(current); /* read completions before cancelations */ inflight = tctx_inflight(tctx, !cancel_all); - if (!inflight) + if (!inflight && !tctx->io_wq) break; if (!sqd) { @@ -3326,20 +3337,25 @@ __cold void io_uring_cancel_generic(bool cancel_all, struct io_sq_data *sqd) if (node->ctx->sq_data) continue; loop |= io_uring_try_cancel_requests(node->ctx, - current, cancel_all); + current, cancel_all, + &wq_cancelled); } } else { list_for_each_entry(ctx, &sqd->ctx_list, sqd_list) loop |= io_uring_try_cancel_requests(ctx, current, - cancel_all); + cancel_all, + &wq_cancelled); } - if (loop) { + if (!wq_cancelled || (inflight && loop)) { cond_resched(); continue; } + if (!inflight) + break; + prepare_to_wait(&tctx->wait, &wait, TASK_INTERRUPTIBLE); io_run_task_work(); io_uring_drop_tctx_refs(current); -- 2.41.0
