Re: 回复: [PATCH] USB: usblp: Add device status detection in usblp_poll()

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On Mon, Mar 01, 2021 at 08:26:22AM +0000, Zhang, Qiang wrote:
> 
> 
> ________________________________________
> 发件人: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
> 发送时间: 2021年3月1日 16:00
> 收件人: Zhang, Qiang
> 抄送: zaitcev@xxxxxxxxxx; linux-usb@xxxxxxxxxxxxxxx
> 主题: Re: [PATCH] USB: usblp: Add device status detection in usblp_poll()
> 
> [Please note: This e-mail is from an EXTERNAL e-mail address]
> 
> On Mon, Mar 01, 2021 at 12:03:00PM +0800, qiang.zhang@xxxxxxxxxxxxx wrote:
> > From: Zqiang <qiang.zhang@xxxxxxxxxxxxx>
> >
> > If usblp device has been disconnected, direct return
> > 'EPOLLHUP | EPOLLERR' in usblp_poll().
> >
> >Why?  What problem are you solving here?  Is this fixing an >older
> >commit, if so, what one?
> >
> 
> There is not need fix older commit.
> After the device is disconnected, if the userspace call poll/select() function, will block and never be awakened .

If the device is disconnected, how can the file be opened at all?
Shouldn't it have been torn down already?

And now you are holding a lock across some poll_wait() calls, is that
going to cause problems?

thanks,

greg k-h



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