From: Jens Axboe axboe@kernel.dk
mainline inclusion from mainline-5.9-rc1 commit 0ba9c9edcd152158a0e321a4c13ac1dfc571ff3d category: feature bugzilla: https://bugzilla.openeuler.org/show_bug.cgi?id=27 CVE: NA ---------------------------
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
Conflicts: fs/io_uring.c [commit c2c4c83c58cb("io_uring: use new io_req_task_work_add() helper throughout") is not merged] Signed-off-by: yangerkun yangerkun@huawei.com Reviewed-by: zhangyi (F) yi.zhang@huawei.com Signed-off-by: Cheng Jian cj.chengjian@huawei.com --- fs/io_uring.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c index 1a4d3408dd04..3a94a7abba87 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -4048,22 +4048,22 @@ 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) + 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; }