linux-kernel - Re: linux-next: umh: fix processed error when UMH_WAIT_PROC is used seems to break linux bridge on s390x (bisected)

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Date:   Wed, 24 Jun 2020 13:17:25 +0000
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     Christian Borntraeger <borntraeger@...ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Martin Doucha <mdoucha@...e.cz>
Cc:     ast@...nel.org, axboe@...nel.dk, bfields@...ldses.org,
        bridge@...ts.linux-foundation.org, chainsaw@...too.org,
        christian.brauner@...ntu.com, chuck.lever@...cle.com,
        davem@...emloft.net, dhowells@...hat.com,
        gregkh@...uxfoundation.org, jarkko.sakkinen@...ux.intel.com,
        jmorris@...ei.org, josh@...htriplett.org, keescook@...omium.org,
        keyrings@...r.kernel.org, kuba@...nel.org,
        lars.ellenberg@...bit.com, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-nfs@...r.kernel.org,
        linux-security-module@...r.kernel.org, nikolay@...ulusnetworks.com,
        philipp.reisner@...bit.com, ravenexp@...il.com,
        roopa@...ulusnetworks.com, serge@...lyn.com, slyfox@...too.org,
        viro@...iv.linux.org.uk, yangtiezhu@...ngson.cn,
        netdev@...r.kernel.org, markward@...ux.ibm.com,
        linux-s390 <linux-s390@...r.kernel.org>
Subject: Re: linux-next: umh: fix processed error when UMH_WAIT_PROC is used
 seems to break linux bridge on s390x (bisected)

Martin, your eyeballs would be appreciated for a bit on this.

On Wed, Jun 24, 2020 at 12:05:46PM +0000, Luis Chamberlain wrote:
> On Wed, Jun 24, 2020 at 01:11:54PM +0200, Christian Borntraeger wrote:
> > 
> > 
> > On 23.06.20 16:23, Christian Borntraeger wrote:
> > > 
> > > 
> > > On 23.06.20 16:11, Christian Borntraeger wrote:
> > >> Jens Markwardt reported a regression in the linux-next runs.  with "umh: fix
> > >> processed error when UMH_WAIT_PROC is used" (from linux-next) a linux bridge
> > >> with an KVM guests no longer activates :
> > >>
> > >> without patch
> > >> # ip addr show dev virbr1
> > >> 6: virbr1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
> > >>     link/ether 52:54:00:1e:3f:c0 brd ff:ff:ff:ff:ff:ff
> > >>     inet 192.168.254.254/24 brd 192.168.254.255 scope global virbr1
> > >>        valid_lft forever preferred_lft forever
> > >>
> > >> with this patch the bridge stays DOWN with NO-CARRIER
> > >>
> > >> # ip addr show dev virbr1
> > >> 6: virbr1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue state DOWN group default qlen 1000
> > >>     link/ether 52:54:00:1e:3f:c0 brd ff:ff:ff:ff:ff:ff
> > >>     inet 192.168.254.254/24 brd 192.168.254.255 scope global virbr1
> > >>        valid_lft forever preferred_lft forever
> > >>
> > >> This was bisected in linux-next. Reverting from linux-next also fixes the issue.
> > >>
> > >> Any idea?
> > > 
> > > FWIW, s390 is big endian. Maybe some of the shifts inn the __KW* macros are wrong.
> > 
> > Does anyone have an idea why "umh: fix processed error when UMH_WAIT_PROC is used" breaks the
> > linux-bridge on s390?
> 
> glibc for instance defines __WEXITSTATUS in only one location: bits/waitstatus.h
> and it does not special case it per architecture, so at this point I'd
> have to say we have to look somewhere else for why this is happening.

I found however an LTP bug indicating the need to test for
s390 wait macros [0] in light of a recent bug in glibc for s390.
I am asking for references to that issue given I cannot find
any mention of this on glibc yet.

I'm in hopes Martin might be aware of that mentioned s390 glic bug.

[0] https://github.com/linux-test-project/ltp/issues/605

  Luis