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

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Date:   Thu, 7 Dec 2017 11:35:42 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Alan Stern <stern@...land.harvard.edu>,
        SF Markus Elfring <elfring@...rs.sourceforge.net>,
        USB list <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>,
        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" <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 Thu, Dec 07, 2017 at 08:40:07AM +0100, Geert Uytterhoeven wrote:
> Hi Alan,
> 
> On Wed, Dec 6, 2017 at 11:02 PM, Alan Stern <stern@...land.harvard.edu> wrote:
> > 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.
> 
> If even allocation of 24 bytes fails, lots of other devices and other parts of
> the system will start failing really soon...
> 

Small allocations never fail in the current kernel.

regards,
dan carpenter