From: Jens Axboe <axboe@xxxxxxxxx>
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@xxxxxxxxxxxxxxx # v5.7+
Reported-by: Josef <josef.grieb@xxxxxxxxx>
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/io_uring.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4100,22 +4100,22 @@ 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;
}
