linux-kernel - Re: [PATCH 2/3] virtio_console: fixup potential cpu stall when free unused bufs

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Message-ID: <20230609120332-mutt-send-email-mst@kernel.org>
Date:   Fri, 9 Jun 2023 12:05:50 -0400
From:   "Michael S. Tsirkin" <mst@...hat.com>
To:     Xianting Tian <xianting.tian@...ux.alibaba.com>
Cc:     arei.gonglei@...wei.com, jasowang@...hat.com,
        xuanzhuo@...ux.alibaba.com, herbert@...dor.apana.org.au,
        davem@...emloft.net, amit@...nel.org, arnd@...db.de,
        gregkh@...uxfoundation.org, marcel@...tmann.org,
        johan.hedberg@...il.com, luiz.dentz@...il.com,
        linux-bluetooth@...r.kernel.org,
        virtualization@...ts.linux-foundation.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/3] virtio_console: fixup potential cpu stall when free
 unused bufs

On Fri, Jun 09, 2023 at 09:18:16PM +0800, Xianting Tian wrote:
> Cpu stall issue may happen if device is configured with multi queues
> and large queue depth, so fix it.

"may happen" is ambigous.

So is this: "for virtio-net we were getting
stall on CPU was observed message, this driver is similar
so theoretically the same logic applies"

or is this

"the following error occured: ..... "

?


> Signed-off-by: Xianting Tian <xianting.tian@...ux.alibaba.com>
> ---
>  drivers/char/virtio_console.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index b65c809a4e97..5ec4cf4ea919 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -1935,6 +1935,7 @@ static void remove_vqs(struct ports_device *portdev)
>  		flush_bufs(vq, true);
>  		while ((buf = virtqueue_detach_unused_buf(vq)))
>  			free_buf(buf, true);
> +		cond_resched();
>  	}
>  	portdev->vdev->config->del_vqs(portdev->vdev);
>  	kfree(portdev->in_vqs);
> -- 
> 2.17.1