io_uring: use TWA_SIGNAL for task_work uncondtionally (0ba9c9ed) · Commits · 戴 / test

An earlier commit: ("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>

fs/io_uring.c

+8 −8

Original line number	Diff line number	Diff line
		@@ -1710,22 +1710,22 @@ static int io_req_task_work_add(struct io_kiocb req, struct callback_head cb)
		{
		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)
		if (!(ctx->flags & IORING_SETUP_SQPOLL))
		notify = TWA_SIGNAL;

		ret = task_work_add(tsk, cb, notify);
		if (!ret)
		wake_up_process(tsk);

		return ret;
		}

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