tree c31e05ee6896127dd399360c8d36bc2b72eb5f3a
parent e2452b4bf3c247fbfd759d047e3c5dedfb6f3202
author Christopher Ferris <cferris@google.com> 1432854633 -0700
committer Christopher Ferris <cferris@google.com> 1433193017 -0700

Modify the code to avoid potential deadlocks.

If the signal to dump a thread is never delivered, then it's
possible for a deadlock. The signal handler is responsible for
unlocking and deleting the ThreadEntry created for the pid/tid
combination. This means if the signal is lost, the ThreadEntry
gets stuck locked and never deleted. If a second attempt to get
a backtrace of this thread occurs, there is a deadlock.

Also, decrease the timeout from 10 seconds to 5 seconds. The original
10 seconds was because the unwind was actually done in the signal
handler. Now the signal handler does nothing but copy the ucontext
structure and let the caller do the unwind.

Bug: 21086132
(cherry picked from commit 2d09171758b7d98c77f27e439a4caf35dd84c311)

Change-Id: I414c500eb08983a5017caf3fce4f499465575a9d