linux-kernel - Re: [PATCH v4] net: usb: ax88179_178a: avoid failed operations when device is disconnected

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Message-ID: <20231206121732.7154-1-jtornosm@redhat.com>
Date:   Wed,  6 Dec 2023 13:17:32 +0100
From:   Jose Ignacio Tornos Martinez <jtornosm@...hat.com>
To:     stern@...land.harvard.edu
Cc:     davem@...emloft.net, edumazet@...gle.com, greg@...ah.com,
        jtornosm@...hat.com, kuba@...nel.org, linux-kernel@...r.kernel.org,
        linux-usb@...r.kernel.org, netdev@...r.kernel.org,
        oneukum@...e.com, pabeni@...hat.com, stable@...r.kernel.org
Subject: Re: [PATCH v4] net: usb: ax88179_178a: avoid failed operations when device is disconnected

Hello Alan,

> The __ax88179_read_cmd() and __ax88179_write_cmd() routines are 
> asynchronous with respect to ax88179_disconnect(), right?  Or at least, 
> they are if they run as a result of the user closing the network 
> interface.  Otherwise there wouldn't be any memory ordering issues.
Yes, I think so, they could be asynchronous regarding ax88179_disconnect.

> But the memory barriers you added are not the proper solution.  What you 
> need here is _synchronization_, not _ordering_.  As it is, the memory 
> barriers you have added don't do anything; they shouldn't be in the 
> patch.
Ok, thank you for the helpful clarification, let me check it better,
I understood it in a wrong way.

> If you would like a more in-depth explanation, let me know.
Thank you for your help, I will try first, I really appreciate this.

Best regards
José Ignacio