dkms issue with "ps -o lstart" under SLES9
Silacci, Lucas
Lucas.Silacci at Teradata.Com
Tue Aug 21 12:01:48 CDT 2007
As a follow-up to my previous post, I understand that the root issue
seems to be a problem with SLES (lstart not staying constant), but I'm
curious as to why the timestamp check is necessary to begin with.
Why not just use the module name/version and process id of the rpm
process?
Thanks!
-Lucas
> -----Original Message-----
> From: dkms-devel-bounces at dell.com
> [mailto:dkms-devel-bounces at dell.com] On Behalf Of Silacci, Lucas
> Sent: Monday, August 20, 2007 5:33 PM
> To: DKMS-devel at dell.com
> Subject: dkms issue with "ps -o lstart" under SLES9
>
> Hello,
>
> I just ran into an issue during an rpm upgrade of my dkms
> driver package and I was wondering if anybody else had seen
> this. During the upgrade a "dkms remove" in my packages
> "%preun" was executed even though it was called with
> "--rpm_safe_upgrade".
>
> For background, I discovered this on SLES9 SP3 with
> dkms-2.0.13-1 installed (although it looks like the latest
> version would be susceptible to the same issue).
>
> I looked at the code and was able to get a debug trace of
> what happened.
> Basically dkms is using the output from "ps -o lstart" to
> help determine that a "dkms remove" command is coming from
> the same rpm process that just did a "dkms add" command
> during an rpm upgrade. It puts the output of the "ps -o
> lstart" into the lockfile and then references that lockfile
> later to see if we are in an "rpm_safe_upgrade" situation.
>
> However, it turns out that the output from that command is
> actually not guaranteed to be identical for the same process
> from call to call under SLES9. I'm not sure about other
> distros, but it's very obviously not safe to use in this
> case. Here's an example of a random process that I
> picked:
>
> samoa2:~ # ps -o lstart 24135
> STARTED
> Thu Aug 16 10:13:20 2007
> samoa2:~ # ps -o lstart 24135
> STARTED
> Thu Aug 16 10:13:19 2007
> samoa2:~ # ps -o lstart 24135
> STARTED
> Thu Aug 16 10:13:19 2007
> samoa2:~ # ps -o lstart 24135
> STARTED
> Thu Aug 16 10:13:19 2007
> samoa2:~ # ps -o lstart 24135
> STARTED
> Thu Aug 16 10:13:20 2007
>
> So I was wondering if anyone else has seen this issue and
> whether there's any plans for a change to dkms for this.
>
> Thanks,
> -Lucas
>
> Here's the dirty details...
>
> There are two relevant pieces of code in dkms:
>
> #1 (where the lock file gets created):
>
> # Do stuff for --rpm_safe_upgrade
> if [ -n "$rpm_safe_upgrade" ]; then
> local pppid=`sed -ne 's/PPid:[ \t]*//p' /proc/$PPID/status`
> local temp_dir_name=`mktemp
> $tmp_location/dkms_rpm_safe_upgrade_lock.$pppid.XXXXXX 2>/dev/null`
> echo "$module-$module_version" >> $temp_dir_name
> ps -o lstart --no-headers -p $pppid 2>/dev/null >>
> $temp_dir_name
> fi
>
> #2 (where we jump out for a safe upgrade):
>
> # Do --rpm_safe_upgrade check (exit out and don't do
> remove if inter-release RPM upgrade scenario occurs)
> if [ -n "$rpm_safe_upgrade" ]; then
> local pppid=`cat /proc/$PPID/status | grep PPid: |
> awk {'print $2'}`
> local time_stamp=`ps -o lstart --no-headers -p $pppid
> 2>/dev/null`
> for lock_file in `ls
> $tmp_location/dkms_rpm_safe_upgrade_lock.$pppid.* 2>/dev/null`; do
> lock_head=`head -n 1 $lock_file 2>/dev/null`
> lock_tail=`tail -n 1 $lock_file 2>/dev/null`
> if [ "$lock_head" == "$module-$module_version"
> ] && [ "$lock_tail" == "$time_stamp" ] && [ -n "$time_stamp" ]; then
> echo $""
> echo $"DKMS: Remove cancelled because
> --rpm_safe_upgrade scenario detected."
> rm -f $lock_file
> exit 0
> fi
> done
> fi
>
> You can see the problem with "ps -o lstart" in the following
> debug output...
>
> Debug output from a good run:
>
> #1 (lstart is saved here):
>
> + '[' -n true ']'
> ++ sed -ne 's/PPid:[ \t]*//p' /proc/25854/status
> + local pppid=25852
> ++ mktemp /tmp/dkms_rpm_safe_upgrade_lock.25852.XXXXXX
> + local temp_dir_name=/tmp/dkms_rpm_safe_upgrade_lock.25852.R25991
> + echo e1000-7.5.5-1
> + ps -o lstart --no-headers -p 25852
>
> #2 (lstart is compared here and everything is fine):
>
> + '[' -n true ']'
> ++ cat /proc/26683/status
> ++ grep PPid:
> ++ awk '{print $2}'
> + local pppid=25852
> ++ ps -o lstart --no-headers -p 25852
> + local 'time_stamp=Mon Aug 20 15:07:16 2007'
> ++ ls /tmp/dkms_rpm_safe_upgrade_lock.25852.R25991
> ++ head -n 1 /tmp/dkms_rpm_safe_upgrade_lock.25852.R25991
> + lock_head=e1000-7.5.5-1
> ++ tail -n 1 /tmp/dkms_rpm_safe_upgrade_lock.25852.R25991
> + lock_tail=Mon Aug 20 15:07:16 2007
> + '[' e1000-7.5.5-1 == e1000-7.5.5-1 ']'
> + '[' 'Mon Aug 20 15:07:16 2007' == 'Mon Aug 20 15:07:16 2007' ']'
> + '[' -n 'Mon Aug 20 15:07:16 2007' ']'
> + echo ''
>
> + echo 'DKMS: Remove cancelled because --rpm_safe_upgrade scenario
> detected.'
> DKMS: Remove cancelled because --rpm_safe_upgrade scenario detected.
> + rm -f /tmp/dkms_rpm_safe_upgrade_lock.25852.R25991
> + exit 0
>
> Debug output from a bad run:
>
> #1 (grabs lstart here):
>
> + '[' -n true ']'
> ++ sed -ne 's/PPid:[ \t]*//p' /proc/28496/status
> + local pppid=28494
> ++ mktemp /tmp/dkms_rpm_safe_upgrade_lock.28494.XXXXXX
> + local temp_dir_name=/tmp/dkms_rpm_safe_upgrade_lock.28494.y28633
> + echo e1000-7.5.5-1
> + ps -o lstart --no-headers -p 28494
>
> #2 (compares incorrectly here):
>
> + '[' -n true ']'
> ++ cat /proc/29326/status
> ++ grep PPid:
> ++ awk '{print $2}'
> + local pppid=28494
> ++ ps -o lstart --no-headers -p 28494
> + local 'time_stamp=Mon Aug 20 15:10:32 2007'
> ++ ls /tmp/dkms_rpm_safe_upgrade_lock.28494.y28633
> ++ head -n 1 /tmp/dkms_rpm_safe_upgrade_lock.28494.y28633
> + lock_head=e1000-7.5.5-1
> ++ tail -n 1 /tmp/dkms_rpm_safe_upgrade_lock.28494.y28633
> + lock_tail=Mon Aug 20 15:10:31 2007
> + '[' e1000-7.5.5-1 == e1000-7.5.5-1 ']'
> + '[' 'Mon Aug 20 15:10:31 2007' == 'Mon Aug 20 15:10:32 2007' ']'
>
> Since the times don't match exactly, my dkms driver gets removed.
>
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