** Summary changed:
- edgy installer randomly hangs on Core 2 Duo, Dell D620
+ debconf-apt-progress hangs sometimes on SMP systems due to racy debconf
protocol handling
** Description changed:
- No more specific information to add than the title. Both the amd64 and
- i386 alternate cds hang during package selection\installation. No
- useful information in dmesg or the installer log.
+ debconf-apt-progress is a helper program used by the installer to run
+ apt-get and turn its progress output into debconf progress bar commands,
+ while passing through any genuine debconf interaction by the packages
+ being installed. Ever since I originally wrote it, that passthrough
+ function has been handled incorrectly: it simply passes through its
+ debconf file descriptors to the child process, which means that child
+ processes may collide with debconf-apt-progress itself while
+ communicating with debconf.
- Debian netinst daily from 28-Sep-2006 runs fine on the same machine, and
- memtest doesnt report any problems.
+ The effect of this is that users installing on SMP systems experience
+ sporadic hangs during the pkgsel step of d-i ("Select and install
+ software"). Since it is a race, frequencies vary; I've heard 30%
+ recently from one person installing on a large number of machines at
+ once. There is absolutely no indication of what has gone wrong, so it
+ gives a very bad impression, and I think therefore it is worth fixing
+ this in Ubuntu 6.06.2.
+
+ I believe that this has been fixed in debconf 1.5.14 in Debian unstable
+ and Ubuntu gutsy. While the patch is substantial as it reorganises
+ debconf-apt-progress' main loop, it operates by opening two additional
+ pipes for the command and reply ends of the debconf protocol, and
+ serialising apt status messages and debconf protocol messages using a
+ select loop, ensuring that collisions cannot occur. I am still actively
+ soliciting testing to confirm that this fixes the bug experienced by
+ users and does not regress.
+
+ Since this is a race, I cannot provide cast-iron instructions on
+ reproducing the bug. However, installing several times (ideally
+ automated with a fresh disk) on a multi-processor system should be
+ sufficient to hit it eventually.
+
+ The only code outside the installer that uses debconf-apt-progress is
+ tasksel. Thus, unless one is using tasksel regularly (which is
+ relatively rare), this patch is not likely to have any effect on
+ upgraders. If it goes wrong, the consequences are likely to be similar
+ to the original bug, i.e. hangs in the pkgsel step of d-i.
** Attachment added: "patch applicable to dapper"
http://launchpadlibrarian.net/8718542/debconf.dapper-proposed.diff
** Description changed:
debconf-apt-progress is a helper program used by the installer to run
apt-get and turn its progress output into debconf progress bar commands,
while passing through any genuine debconf interaction by the packages
being installed. Ever since I originally wrote it, that passthrough
function has been handled incorrectly: it simply passes through its
debconf file descriptors to the child process, which means that child
processes may collide with debconf-apt-progress itself while
- communicating with debconf.
+ communicating with debconf. This bug is present in all releases since
+ Ubuntu 6.06.
The effect of this is that users installing on SMP systems experience
sporadic hangs during the pkgsel step of d-i ("Select and install
software"). Since it is a race, frequencies vary; I've heard 30%
recently from one person installing on a large number of machines at
once. There is absolutely no indication of what has gone wrong, so it
gives a very bad impression, and I think therefore it is worth fixing
this in Ubuntu 6.06.2.
I believe that this has been fixed in debconf 1.5.14 in Debian unstable
and Ubuntu gutsy. While the patch is substantial as it reorganises
debconf-apt-progress' main loop, it operates by opening two additional
pipes for the command and reply ends of the debconf protocol, and
serialising apt status messages and debconf protocol messages using a
select loop, ensuring that collisions cannot occur. I am still actively
soliciting testing to confirm that this fixes the bug experienced by
users and does not regress.
+ https://bugs.launchpad.net/ubuntu/+source/debconf/+bug/62986/comments/16
+ links to the patch I applied to the test CD images linked to from this
+ bug.
Since this is a race, I cannot provide cast-iron instructions on
reproducing the bug. However, installing several times (ideally
automated with a fresh disk) on a multi-processor system should be
sufficient to hit it eventually.
The only code outside the installer that uses debconf-apt-progress is
tasksel. Thus, unless one is using tasksel regularly (which is
relatively rare), this patch is not likely to have any effect on
upgraders. If it goes wrong, the consequences are likely to be similar
to the original bug, i.e. hangs in the pkgsel step of d-i.
--
debconf-apt-progress hangs sometimes on SMP systems due to racy debconf
protocol handling
https://bugs.launchpad.net/bugs/62986
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