Re: [PATCH 1/1] virtio_net: Add timeout handler to avoid kernel hang

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在 2024/1/20 1:29, Andrew Lunn 写道:
       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


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