Date: Wed, 22 Jun 2005 11:21:18 -0400 From: John Baldwin <jhb@FreeBSD.org> To: freebsd-hackers@freebsd.org Cc: Stefan Farfeleder <stefan@fafoe.narf.at>, Juho Vuori <juho.vuori@kepa.fi> Subject: Re: Bug in devinfo or something wrong with me? Message-ID: <200506221121.19848.jhb@FreeBSD.org> In-Reply-To: <200506211116.32625.jhb@FreeBSD.org> References: <42887FEE.3000705@kepa.fi> <20050516125109.GF33622@wombat.fafoe.narf.at> <200506211116.32625.jhb@FreeBSD.org>
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On Tuesday 21 June 2005 11:16 am, John Baldwin wrote:
> On Monday 16 May 2005 08:51 am, Stefan Farfeleder wrote:
> > On Mon, May 16, 2005 at 02:11:42PM +0300, Juho Vuori wrote:
> > > The below included simple program reliably printfs "error 4\n" on
> > > 5.4-RELEASE. Am I understanding something wrong or is this a bug in
> > > libdevinfo?
> >
> > There is indeed a bug in libdevinfo.
> >
> > > To continue on this however, if you put say sleep(5) between
> > > devinfo_free() and the second devinfo_init() and manage to change the
> > > device configuration during the sleep (tested with pluggin in/out a USB
> > > memory), the program terminates with no errors. I've run into other
> > > oddities with devinfo as well, but in much more complex situations so
> > > they might just as well be variations of this simple example.
> > >
> > > if (devinfo_init()) {
> >
> > devinfo_init() initialises the devinfo_dev tailq, devinfo_generation and
> > sets devinfo_initted to 1.
> >
> > > devinfo_free();
> >
> > devinfo_free() clears devinfo_dev and sets devinfo_initted to 0 but
> > devinfo_generation keeps its value.
> >
> > > if (devinfo_init()) {
> >
> > Now devinfo_dev doesn't get filled because ubus.ub_generation ==
> > devinfo_generation.
> >
> > Here is a patch that resets devinfo_generation to 0 in devinfo_free().
> > The whole file can probably be simplified a bit due to this bug.
> >
> > Stefan
>
> I think the intent is actually so that you can call devinfo_init()
> periodically without calling devinfo_free() to make sure the tree is up to
> date. However, the generation should still be cleared when free() is
> called. IOW, if you wanted to have a program that would poll the kernel
> each second to get the current tree, it would call devinfo_init() in a loop
> and only call devinfo_free() at program exit. This would let
> devinfo_init() cache data if the device tree doesn't change. I'll try to
> get the patch into the tree.
I just committed it to HEAD and will MFC in a week or so.
--
John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/
"Power Users Use the Power to Serve" = http://www.FreeBSD.org
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