Re: device_cio_free.conf

[Dan Horák]

Waiki Wright píše v Út 06. 09. 2011 v 18:27 -0400: 
>  Hello Dan,
>  I saw your name in one of the bugs related to device_cio_free.conf and 
>  hope that you may be able to answer my question.  If you prefer me to 
>  send my inquire to a mailing list, please let me know. 
I'm sending the reply to mailing list, so more people can comment.

>  I am using s390utils-1.8.2-28.el6.s390x package and I am wondering if
>
>  there will be a race condition between rcS and device_cio_free.
>  
>  The device_cio_free.conf file said that it will start when rcS.conf is 
>  starting:
>  #
>  # free all devices on startup
>  #
>  
>  start on starting rcS
>  
>  task
>  
>  console output
>  
>  exec /sbin/device_cio_free
>  
>  However, in the /sbin/device_cio_free script,  it depends on /proc is 
>  mounted before the script is called:
>  
>  BLACKLIST=/proc/cio_ignore
>  .
>  .
>  .
>  if [ ! -f $BLACKLIST ]; then
>       echo "Error: $BLACKLIST kernel interface doesn't exist"
>       exit 2
>  fi
>  
>  If the file system is mounted later (from rcS), then device_cio_free 
>  script will fail.  So should it be better if
>  device_cio_free.conf to start on after /proc is mounted?
>  
>  Your thought? 
Your conclusion looks logical. However this upstart job was proposed by
our upstart maintainer when I asked him for a solution to the following
problem: need to start an action before the system will try to mount
non-root filesystem devices or bring network interfaces up. Also it
shouldn't interfere with the startup process on primary arches.

Staring with Fedora 15 there is a systemd solution, see
device_cio_free.service in s390utils-1.14.0-1.fc16 [1]


Dan

[1] http://s390.koji.fedoraproject.org/koji/buildinfo?buildID=74738

device_cio_free.conf

[Waiki Wright]

On 09/07/2011 05:17 AM, Dan Horák wrote:
>  Waiki Wright píše v Út 06. 09. 2011 v 18:27 -0400:
> > Hello Dan,
> > I saw your name in one of the bugs related to device_cio_free.conf and
> > hope that you may be able to answer my question.  If you prefer me to
> > send my inquire to a mailing list, please let me know.
>  I'm sending the reply to mailing list, so more people can comment.
>
> > I am using s390utils-1.8.2-28.el6.s390x package and I am wondering if
> > there will be a race condition between rcS and device_cio_free.
> >
> > The device_cio_free.conf file said that it will start when rcS.conf is
> > starting:
> > #
> > # free all devices on startup
> > #
> >
> > start on starting rcS
> >
> > task
> >
> > console output
> >
> > exec /sbin/device_cio_free
> >
> > However, in the /sbin/device_cio_free script,  it depends on /proc is
> > mounted before the script is called:
> >
> > BLACKLIST=/proc/cio_ignore
> > .
> > .
> > .
> > if [ ! -f $BLACKLIST ]; then
> >       echo "Error: $BLACKLIST kernel interface doesn't exist"
> >       exit 2
> > fi
> >
> > If the file system is mounted later (from rcS), then device_cio_free
> > script will fail.  So should it be better if
> > device_cio_free.conf to start on after /proc is mounted?
> >
> > Your thought?
>  Your conclusion looks logical. However this upstart job was proposed by
>  our upstart maintainer when I asked him for a solution to the following
>  problem: need to start an action before the system will try to mount
>  non-root filesystem devices or bring network interfaces up. Also it
>  shouldn't interfere with the startup process on primary arches.
>
>  Staring with Fedora 15 there is a systemd solution, see
>  device_cio_free.service in s390utils-1.14.0-1.fc16 [1]
>
>
>  Dan
>
>  [1] http://s390.koji.fedoraproject.org/koji/buildinfo?buildID=74738
>  
Hi Dan,
Even with the systemd implementation, there is still a possibility for 
the race condition that I mentioned above(let me know if I am wrong).  I 
haven't seen any response for my question and I wonder if this is a 
potential problem that worth for a fix.

Waiki

device_cio_free.conf

[Waiki Wright]

Dan,
During the start up sequence, I encountered this error message (which 
came from device_cio_free script)

Error: /proc/cio_ignore kernel interface doesn't exist

And it is certainly comes from the race condition that I mentioned before.

I applied the following "in-house" patches and the error message went away:

  diff -Npur rcS.conf.orig rcS.conf
--- rcS.conf.orig       2011-08-18 19:58:06.998420543 +0200
+++ rcS.conf    2011-10-04 23:04:35.385850069 +0200
@@ -14,6 +14,7 @@ task
  console output
  exec /etc/rc.d/rc.sysinit
  post-stop script
+        initctl emit --no-wait procmounted
         if [ "$UPSTART_EVENTS" = "startup" ]; then
                 [ -f /etc/inittab ] && runlevel=$(/bin/awk -F ':' '$3

== "initdefault" && $1 !~ "^#" { print $2 }'
/etc/inittab)
                 [ -z "$runlevel" ] && runlevel="3"


diff -Npur device_cio_free.conf.orig
device_cio_free.conf
--- device_cio_free.conf.orig   2011-08-18 19:57:54.568472020 +0200
+++ device_cio_free.conf        2011-08-18 20:00:23.478419433 +0200
@@ -2,7 +2,8 @@
  # free all devices on startup
  #

-start on starting rcS
+#Start when /proc is mounted
+start on procmounted

  task

Any comments?
We are temporary using these "in-house" patches until we hear more from 
you in regard to a possible solution.

Thanks!
Waiki

device_cio_free.conf

[Dan Horák]

Waiki Wright píše v Pá 23. 09. 2011 v 14:16 -0400: 
>  On 09/07/2011 05:17 AM, Dan Horák wrote:
>  > Waiki Wright píše v Út 06. 09. 2011 v 18:27 -0400:
>  >> Hello Dan,
>  >> I saw your name in one of the bugs related to device_cio_free.conf and
>  >> hope that you may be able to answer my question.  If you prefer me to
>  >> send my inquire to a mailing list, please let me know.
>  > I'm sending the reply to mailing list, so more people can comment.
>  >
>  >> I am using s390utils-1.8.2-28.el6.s390x package and I am wondering if
>  >> there will be a race condition between rcS and device_cio_free.
>  >>
>  >> The device_cio_free.conf file said that it will start when rcS.conf is
>  >> starting:
>  >> #
>  >> # free all devices on startup
>  >> #
>  >>
>  >> start on starting rcS
>  >>
>  >> task
>  >>
>  >> console output
>  >>
>  >> exec /sbin/device_cio_free
>  >>
>  >> However, in the /sbin/device_cio_free script,  it depends on /proc is
>  >> mounted before the script is called:
>  >>
>  >> BLACKLIST=/proc/cio_ignore
>  >> .
>  >> .
>  >> .
>  >> if [ ! -f $BLACKLIST ]; then
>  >>       echo "Error: $BLACKLIST kernel interface doesn't exist"
>  >>       exit 2
>  >> fi
>  >>
>  >> If the file system is mounted later (from rcS), then device_cio_free
>  >> script will fail.  So should it be better if
>  >> device_cio_free.conf to start on after /proc is mounted?
>  >>
>  >> Your thought?
>  > Your conclusion looks logical. However this upstart job was proposed by
>  > our upstart maintainer when I asked him for a solution to the following
>  > problem: need to start an action before the system will try to mount
>  > non-root filesystem devices or bring network interfaces up. Also it
>  > shouldn't interfere with the startup process on primary arches.
>  >
>  > Staring with Fedora 15 there is a systemd solution, see
>  > device_cio_free.service in s390utils-1.14.0-1.fc16 [1]
>  >
>  >
>  > Dan
>  >
>  > [1] http://s390.koji.fedoraproject.org/koji/buildinfo?buildID=74738
>  >
>  Hi Dan,
>  Even with the systemd implementation, there is still a possibility for 
>  the race condition that I mentioned above(let me know if I am wrong).  I 
>  haven't seen any response for my question and I wonder if this is a 
>  potential problem that worth for a fix. 
race conditions are always serious issue and when they can be reproduced
it's definitely worth to open a bugzilla. I'd suggest to fill one
against both RHEL-6 and Fedora.


Dan

device_cio_free.conf

[Dan Horák]

Waiki Wright píše v Út 04. 10. 2011 v 17:20 -0400: 
>  Dan,
>  During the start up sequence, I encountered this error message (which 
>  came from device_cio_free script)
>  
>  Error: /proc/cio_ignore kernel interface doesn't exist
>  
>  And it is certainly comes from the race condition that I mentioned before.
>  
>  I applied the following "in-house" patches and the error message went away:
>  
>    diff -Npur rcS.conf.orig rcS.conf
>  --- rcS.conf.orig       2011-08-18 19:58:06.998420543 +0200
>  +++ rcS.conf    2011-10-04 23:04:35.385850069 +0200
>  @@ -14,6 +14,7 @@ task
>    console output
>    exec /etc/rc.d/rc.sysinit
>    post-stop script
>  +        initctl emit --no-wait procmounted
>           if [ "$UPSTART_EVENTS" = "startup" ]; then
>                   [ -f /etc/inittab ] && runlevel=$(/bin/awk -F ':'
> '$3 
>  == "initdefault" && $1 !~ "^#" { print $2 }'
> /etc/inittab)
>                   [ -z "$runlevel" ] && runlevel="3"
>  
>  
>  diff -Npur device_cio_free.conf.orig
>  device_cio_free.conf
>  --- device_cio_free.conf.orig   2011-08-18 19:57:54.568472020 +0200
>  +++ device_cio_free.conf        2011-08-18 20:00:23.478419433 +0200
>  @@ -2,7 +2,8 @@
>    # free all devices on startup
>    #
>  
>  -start on starting rcS
>  +#Start when /proc is mounted
>  +start on procmounted
>  
>    task
>  
>  Any comments?
>  We are temporary using these "in-house" patches until we hear more from 
>  you in regard to a possible solution. 
I will point our upstart/initscripts maintainer to this, but for me the
proposed fix makes sense.


Dan