在 2024/1/20 1:29, Andrew Lunn 写道:

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       while (!virtqueue_get_buf(vi->cvq, &tmp) &&
-           !virtqueue_is_broken(vi->cvq))
+           !virtqueue_is_broken(vi->cvq)) {
+        if (timeout)
+            timeout--;

This is not really a timeout, just a loop counter. 200 iterations could
be a very short time on reasonable H/W. I guess this avoid the soft
lockup, but possibly (likely?) breaks the functionality when we need to
loop for some non negligible time.

I fear we need a more complex solution, as mentioned by Micheal in the
thread you quoted.

Got it. I also look forward to the more complex solution to this problem.

Can we add a device capability (new feature bit) such as ctrq_wait_timeout
to get a reasonable timeout？

The usual solution to this is include/linux/iopoll.h. If you can sleep
read_poll_timeout() otherwise read_poll_timeout_atomic().

I read carefully the functions read_poll_timeout() and 
read_poll_timeout_atomic(). The timeout is set by the caller of the 2 
functions.

As such, can we add a module parameter to customize this timeout value 
by the user?

Or this timeout value is stored in device register, virtio_net driver 
will read this timeout value at initialization?

Zhu Yanjun

	Andrew