commit d36967415b521f4f3c1cc4ac2ad8fa1ac02507c9
author Todd Wang <toddw@google.com> Mon Jan 18 13:53:53 2016 -0800
committer Todd Wang <toddw@google.com> Mon Jan 18 13:53:53 2016 -0800
tree 65e62bdc8737aec582133417dd96a0cb2039faea
parent 673c7717bf86a8a67eda09302c1b67cc5eddeb89

gosh: Exit signal-handling goroutine on Cleanup, other cleanups.

I noticed while running tests that we had a bunch of termination
signal handler goroutines running.  It's better to clean up these
goroutines, since they do take up some resources, and more
importantly, clutter up the stack traces on failure.  The new
logic shuts down the goroutine when cleanup is called.  It's hard
to write a test to verify this, since Go doesn't provide a way to
detect that a goroutine has finished.  So I don't have a test.

I also did some minor reorganizing to get better stacktraces from
the goroutines spawned by gosh; basically making sure we had
named functions in the stacktrace to help debugging.

I also noticed that sh.dirStack is used in cleanup, so we need to
ensure sh.cleanupMu is locked when touching it.  I think I missed
this when I added the dirStack to the cleanup.

Finally, I noticed that TestSignal and TestTerminate are flaky,
because of a race between the child process installing the signal
handler, and the test process sending the signal.  I added some
synchronization to avoid this race, and also changed to children
to sleep for 1 hour rather than 1 second, since we're trying to
test the case where they haven't exited yet.

Change-Id: I73a080e781008a1fdcf3401b41d2d5b84e108560