linux-kernel - Re: USB: hub: Delete an error message for a failed memory allocation in usb_hub_clear_tt

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Message-ID: <Pine.LNX.4.44L0.1712061700550.1507-100000@iolanthe.rowland.org>
Date:   Wed, 6 Dec 2017 17:02:40 -0500 (EST)
From:   Alan Stern <stern@...land.harvard.edu>
To:     SF Markus Elfring <elfring@...rs.sourceforge.net>
cc:     linux-usb@...r.kernel.org, Joe Perches <joe@...ches.com>,
        Daniel Drake <drake@...lessm.com>,
        Dmitry Fleytman <dmitry@...nix.com>,
        Eugene Korenevsky <ekorenevsky@...il.com>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Günter Röck <linux@...ck-us.net>,
        Johan Hovold <johan@...nel.org>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Peter Chen <peter.chen@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        <kernel-janitors@...r.kernel.org>
Subject: Re: USB: hub: Delete an error message for a failed memory allocation
 in usb_hub_clear_tt_buffer()

On Wed, 6 Dec 2017, SF Markus Elfring wrote:

> >>> Does the existing memory allocation error message include the 
> >>> &udev->dev device name and driver name?  If it doesn't, there will be 
> >>> no way for the user to tell that the error message is related to the 
> >>> device failure.
> >>
> >> No, but the effect is similar.
> >>
> >> OOM does a dump_stack() so this function's call tree is shown.
> > 
> > A call stack doesn't tell you which device was being handled.
> 
> Do you find a default Linux allocation failure report insufficient then?
> 
> Would you like to to achieve that the requested information can be determined
> from a backtrace?

It is not practical to do this.  The memory allocation routines do not 
for what purpose the memory is being allocated; hence when a failure 
occurs they cannot tell what device (or other part of the system) will 
be affected.

That's why we have a secondary error message.

Alan Stern