[PATCH 5.7 356/393] io_uring: use TWA_SIGNAL for task_work uncondtionally
flat view
STALE2248d
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Date: 2020-08-17 18:37:40
Also in:
lkml
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 <redacted>
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; }