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Re: kern/48243 (inconsistant usage of 'up->parent' in usb_subr.c)

The following reply was made to PR kern/48243; it has been noted by GNATS.

From: Wolfgang Stukenbrock <>
To: <>
Cc: <>, <>, <>,
        <>, <>
Subject: Re: kern/48243 (inconsistant usage of 'up->parent' in usb_subr.c)
Date: Fri, 14 Oct 2016 10:56:12 +0200

 Hi, sorry for the delay, but I was offline for a while.
 If a pointer can be NULL and not NULL then it always make sence to check th=
 is (at least in debug-builds) to catch
 any situation where the expected state is not the expected one.
 And if a call to a subroutine 'can (should?)' never fail, this should to be=
  checked to=F6.
 If you think the code is stable enought that it will never fail, you may ad=
 d checks only for debug-builds to validate this.
 This wouldn't harm performance in normal kernels.
 This is my understanding from a 'stable' source that allows searching for e=
 rrors if any happen.
 And perhaps it would be a good idea to add a short comment when the pointer=
  is NULL or not ..
 As stated in the initial report, I found this by analysing a problem I've w=
 ith something in the USB stack.
 It is along time ago and I don't remember the cause why I've a look at it a=
 nymore - sorry.
 As far as I remember, it was never the cause of a kernel crash - in that ca=
 se I haven't classified the report as non-critical/medium.
 On Mon, 3 Oct 2016 06:50:49 +0000
 <> wrote:
 > Synopsis: inconsistant usage of 'up->parent' in usb_subr.c
 > State-Changed-From-To: open->feedback
 > State-Changed-By:
 > State-Changed-When: Mon, 03 Oct 2016 06:50:49 +0000
 > State-Changed-Why:
 > The only time up->up_parent is non-NULL is for a root hub. Here the
 > usbd_get_initial_ddsec can (should?) never fail and therefore the
 > usbd_reset_port won't happen.
 > Is the code as-is really a problem?
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