From: Bjorn Andersson <bjorn.andersson@linaro.org>
To: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
Cc: Lucas De Marchi <lucas.de.marchi@gmail.com>,
linux-modules <linux-modules@vger.kernel.org>,
afaerber@suse.de
Subject: Re: [PATCH] depmod: ignore related modules in depmod_report_cycles
Date: Mon, 7 Nov 2016 12:23:44 -0800 [thread overview]
Message-ID: <20161107202344.GE25787@tuxbot> (raw)
In-Reply-To: <1478539679.8215.31.camel@suse.com>
On Mon 07 Nov 09:27 PST 2016, Mian Yousaf Kaukab wrote:
> On Sat, 2016-11-05 at 21:50 -0200, Lucas De Marchi wrote:
> > Hi,
> >
> > On Fri, Nov 4, 2016 at 7:33 AM, Mian Yousaf Kaukab
> > <yousaf.kaukab@suse.com> wrote:
> > >
> > > Only print actual cyclic dependencies. Don't print count of all the
> > > modules as it includes other modules which have dependencies but
> > > not
> > > necessarily cyclic.
> > >
> > > Printing related modules causes buffer overflow as m->modnamesz is
> > > not
> > > included in buffer size calculations (loop == m is never true).
> > > This buffer overflow causes kmod to crash.
> > >
> > > Reported-by: Andreas F�rber <afaerber@suse.de>
> > > Signed-off-by: Mian Yousaf Kaukab <yousaf.kaukab@suse.com>
> > > ---
> > > As count of modules in cyclic dependency chain is not known at the
> > > start of this function, so it is not printed anymore. The output
> > > when cyclic dependency is detected is changed as following:
> > >
> > > Old:
> > > depmod: ERROR: Found 8 modules in dependency cycles!
> > >
> > > New:
> > > depmod: ERROR: Modules found in dependency cycles!
> >
> > I think it would be good to fix this problem, but retaining the
> > behavior.
> Would it be OK if the modules names are printed first and count is
> printed afterward. Something like following:�
>
> DEPMOD��4.9.0-rc4-default
> depmod: ERROR: Cycle detected: qcom_wcnss_iris -> qcom_wcnss ->
> qcom_wcnss_iris
> depmod: ERROR: Found 2 modules in dependency cycles!
> Makefile:1227: recipe for target '_modinst_post' failed
>
> In this way modules names can still be printed in the loop and then the
> exact count of modules involved in cyclic dependency is printed at the
> end of the depmod_report_cycles().
>
> >
> > My first reaction to this is "how do I reproduce the issue?". This
> > number so far does tell us how many modules are involved in loops.
> There is more info at the following link:
> https://bugzilla.opensuse.org/show_bug.cgi?id=1008186
>
> You can reproduce the issue by enabling�CONFIG_QCOM_WCNSS_PIL as module
> in v4.9-rc4 for arm64.�
> +CONFIG_REMOTEPROC=m
> +CONFIG_QCOM_MDT_LOADER=m
> -# CONFIG_QCOM_WCNSS_PIL is not set
> +CONFIG_QCOM_WCNSS_IRIS=m
> +CONFIG_QCOM_WCNSS_PIL=m
>
I added some debugging prints to track the stack management in
depmod_report_cycles().
remoteproc, mdt_loader, wcnss_iris and wcnss_pil are all roots and we
have dependencies like this.
/---(rproc)
| ^
| |
(pil) -+-> (mdt)
^ |
| v
+- (iris)
1) We pick rproc as first root, mark that as visited and see that we're
done.
2) We pick mdt_loader as second root, we push remoteproc to the stack
and find that it's already visited, so we found a loop!
mdt_loader -> remoteproc
3) We pick iris as third root, we push wcnss which pushes remoteproc,
mdt_loader and iris. All three have already been visited from root #1
and #2, so we find that there's a loop in:
iris -> wcnss -> iris
iris -> wcnss -> mdt
iris -> wcnss -> remoteproc
Only one of these cases are actually a cycle, but as we don't reset
visited between the searches we can't tell. Further more, if there was a
dependency from iris -> remoteproc that would have shown up earlier and
marked iris->visited and when we get to step #3 we would just have
bailed directly - completely missing the cycle.
So I think we need to reset the visited list on each run of the DFS from
each root.
Regards,
Bjorn
next prev parent reply other threads:[~2016-11-07 20:23 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-04 9:33 [PATCH] depmod: ignore related modules in depmod_report_cycles Mian Yousaf Kaukab
2016-11-05 23:50 ` Lucas De Marchi
2016-11-07 17:27 ` Mian Yousaf Kaukab
2016-11-07 20:23 ` Bjorn Andersson [this message]
2016-11-08 9:36 ` Mian Yousaf Kaukab
2016-11-08 17:03 ` Bjorn Andersson
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