| From 0ba9c9edcd152158a0e321a4c13ac1dfc571ff3d Mon Sep 17 00:00:00 2001 |
| From: Jens Axboe <axboe@kernel.dk> |
| Date: Thu, 6 Aug 2020 19:41:50 -0600 |
| Subject: io_uring: use TWA_SIGNAL for task_work uncondtionally |
| |
| From: Jens Axboe <axboe@kernel.dk> |
| |
| commit 0ba9c9edcd152158a0e321a4c13ac1dfc571ff3d upstream. |
| |
| An earlier commit: |
| |
| b7db41c9e03b ("io_uring: fix regression with always ignoring signals in io_cqring_wait()") |
| |
| ensured that we didn't get stuck waiting for eventfd reads when it's |
| registered with the io_uring ring for event notification, but we still |
| have cases where the task can be waiting on other events in the kernel and |
| need a bigger nudge to make forward progress. Or the task could be in the |
| kernel and running, but on its way to blocking. |
| |
| This means that TWA_RESUME cannot reliably be used to ensure we make |
| progress. Use TWA_SIGNAL unconditionally. |
| |
| Cc: stable@vger.kernel.org # v5.7+ |
| Reported-by: Josef <josef.grieb@gmail.com> |
| Signed-off-by: Jens Axboe <axboe@kernel.dk> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| |
| --- |
| fs/io_uring.c | 16 ++++++++-------- |
| 1 file changed, 8 insertions(+), 8 deletions(-) |
| |
| --- a/fs/io_uring.c |
| +++ b/fs/io_uring.c |
| @@ -4161,22 +4161,22 @@ static int io_req_task_work_add(struct i |
| { |
| struct task_struct *tsk = req->task; |
| struct io_ring_ctx *ctx = req->ctx; |
| - int ret, notify = TWA_RESUME; |
| + int ret, notify; |
| |
| /* |
| - * SQPOLL kernel thread doesn't need notification, just a wakeup. |
| - * If we're not using an eventfd, then TWA_RESUME is always fine, |
| - * as we won't have dependencies between request completions for |
| - * other kernel wait conditions. |
| + * SQPOLL kernel thread doesn't need notification, just a wakeup. For |
| + * all other cases, use TWA_SIGNAL unconditionally to ensure we're |
| + * processing task_work. There's no reliable way to tell if TWA_RESUME |
| + * will do the job. |
| */ |
| - if (ctx->flags & IORING_SETUP_SQPOLL) |
| - notify = 0; |
| - else if (ctx->cq_ev_fd) |
| + notify = 0; |
| + if (!(ctx->flags & IORING_SETUP_SQPOLL)) |
| notify = TWA_SIGNAL; |
| |
| ret = task_work_add(tsk, cb, notify); |
| if (!ret) |
| wake_up_process(tsk); |
| + |
| return ret; |
| } |
| |