[Bug 922754] Re: booting without --no-log causes init and plymouth-upstart-bridge to spin at 100%

[Steve Langasek]

Reproducer attached.  I can use this to reliably reproduce the busy loop
on my laptop and in a VM.  So hopefully this provides the clues we need!

In the process of refining this test case, I also repeatedly ran into a
panic (!= EIO assertion failure in log.c), but I haven't been able to
figure out again how to reproduce the error.  Maybe there's another
related bug lingering, or maybe it's a different manifestation of the
same bug.

** Attachment added: "upstart-busyloop.conf"
   https://bugs.launchpad.net/ubuntu/+source/upstart/+bug/922754/+attachment/2700904/+files/upstart-busyloop.conf

** Changed in: upstart (Ubuntu)
       Status: Incomplete => Triaged

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https://bugs.launchpad.net/bugs/922754

Title:
  booting without --no-log causes init and plymouth-upstart-bridge to
  spin at 100%

Status in “upstart” package in Ubuntu:
  Triaged

Bug description:
  Release: Precise
  Architecture: amd64

  Likely broken since upstart_1.4-0ubuntu3

  When booting after recent updates I see init and plymouth-upstart-
  bridge spinning at 100% CPU time, defunct processes do not get reaped
  and a console on ttyS1 which is supposed to start, does not come up.

  Looking at strace of plymouth-upstart-bridge it seems to run a tight loop of 
  epoll_wait(3, {}, 64, 0)                = 0 (/proc/1383/fd/3 -> anon_inode:[eventpoll])

  and init does another tight loop of
  read(24, 0x7ffdc2d1caa0, 8192)          = -1 EAGAIN (Resource temporarily unavailable)
    (/proc/1/fd/24 -> /dev/ptmx)

  Booting with --no-log on the grub commandline brings the system up
  without showing any problems.

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