Cleanup parallel_emerge exit conditions to fix hangs.

Cleanup parallel_emerge exit conditions to fix hangs.

I've cleaned up parallel_emerge to send explicit signals to children to tell
them when they need to exit. I also cleaned up the CTRL-C handling to
correctly print data when interrupted by CTRL-C (previously, the print
thread exited first, so the data we wanted on the failure wasn't
actually printed.)

BUG=chromium-os:5976
TEST=Test several board emerges, including exiting early with CTRL-C.

Change-Id: Iab6efc8e1bf868106244a6210bd02e9e8283af37

Committed: http://chrome-svn/viewvc/chromeos?view=rev&revision=145b4e0

[davidjames, 2010-10-02 21:40:04]

This should hopefully fix our hanging bugs.

[Nick Sanders, 2010-10-06 17:36:22]

lgtm with fixes

http://codereview.chromium.org/3534006/diff/1/2
File parallel_emerge (right):

http://codereview.chromium.org/3534006/diff/1/2#newcode1312
parallel_emerge:1312: if not target:
Can you add more comments that null target indicates exit, and that you are
recycling it through the task queue to get everyone to quit.

http://codereview.chromium.org/3534006/diff/1/2#newcode1425
parallel_emerge:1425: signal.signal(signal.SIGINT, signal.SIG_DFL)
should this be sigterm?

http://codereview.chromium.org/3534006/diff/1/2#newcode1437
parallel_emerge:1437: job.Print(seek_locations)
can you add a comment about what seek_locations is and how Print sets it

http://codereview.chromium.org/3534006/diff/1/2#newcode1584
parallel_emerge:1584: self._emerge_queue.put(None)
Also, comment that None object == exit message

http://codereview.chromium.org/3534006/diff/1/2#newcode1588
parallel_emerge:1588: # Kill print queue.
also comment about how print queue must run until after all other threads close

[David James, 2010-10-06 17:48:15]

http://codereview.chromium.org/3534006/diff/1/2
File parallel_emerge (right):

http://codereview.chromium.org/3534006/diff/1/2#newcode1312
parallel_emerge:1312: if not target:
On 2010/10/06 17:36:25, Nick Sanders wrote:
> Can you add more comments that null target indicates exit, and that you are
> recycling it through the task queue to get everyone to quit.

Done.

http://codereview.chromium.org/3534006/diff/1/2#newcode1425
parallel_emerge:1425: signal.signal(signal.SIGINT, signal.SIG_DFL)
On 2010/10/06 17:36:25, Nick Sanders wrote:
> should this be sigterm?

Done.

http://codereview.chromium.org/3534006/diff/1/2#newcode1437
parallel_emerge:1437: job.Print(seek_locations)
On 2010/10/06 17:36:25, Nick Sanders wrote:
> can you add a comment about what seek_locations is and how Print sets it

Done.

http://codereview.chromium.org/3534006/diff/1/2#newcode1584
parallel_emerge:1584: self._emerge_queue.put(None)
On 2010/10/06 17:36:25, Nick Sanders wrote:
> Also, comment that None object == exit message

Done.

http://codereview.chromium.org/3534006/diff/1/2#newcode1588
parallel_emerge:1588: # Kill print queue.
On 2010/10/06 17:36:25, Nick Sanders wrote:
> also comment about how print queue must run until after all other threads
close

Done.