linux-kernel - Re: Possible hungtask issue will be introduced with device_lock() in uevent

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Message-ID: <2024123128-monetize-outtakes-3260@gregkh>
Date: Tue, 31 Dec 2024 09:26:49 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Zhang Zekun <zhangzekun11@...wei.com>
Cc: dan.j.williams@...el.com, linux-kernel@...r.kernel.org,
	rafael.j.wysocki@...el.com, regressions@...ts.linux.dev,
	tj@...nel.org, alex.williamson@...hat.com, chenjun102@...wei.com
Subject: Re: Possible hungtask issue will be introduced with device_lock() in
 uevent_show()

On Tue, Dec 31, 2024 at 03:56:08PM +0800, Zhang Zekun wrote:
> Hi, Dan, Greg,
> 
> We have found a potential tungtask issue has been introduce by commit 9a71892cbcdb ("Revert "driver core: Fix uevent_show() vs driver detach race""), which revert the rcu in device_uevent but reintroduce the device_lock() in uevent_show(). The reproduce procedure is quite simple:

The revert just puts the original logic back in place, so this is not
anything new that has been introduced, right?  It's just that the
attempted fix didn't work, so a different fix needs to happen.

If you could help debug the original fix, that would be most appreciated
as none of us here are arguing that there isn't a bug present, only that
the fix caused different problems which required it to be reverted.

thanks,

greg k-h