tree a0c03a28963cf6683b3832cf4548b4bf8961b912
parent 3188d117d6f1ba5f3a30d0ff231d816ebb59a7f7
author Sebastien Hertz <shertz@google.com> 1392829217 +0100
committer Sebastien Hertz <shertz@google.com> 1392906181 +0100

Fix deoptimization deadlock

Fixes a deadlock occuring during undeoptimization on debugging session end.

Before disconnecting debugger, we must unregister all requested events. We take
the event list lock to browse all these events. Some of them (as METHOD_EXIT)
may have activated deoptimization so we need to undeoptimize. During this
process, we restore all original entrypoints of every method in the stack and
notify method exit events to the instrumentation listener (see method
InstrumentationLister::MethodExited). In our case, the instrumentation listener
is the debugger. It takes the event list lock (to browse the event list and see
if this event must be posted) but hangs waiting for it. Since it's already
holding the event list lock (which is not recursive), it ends up in a deadlock
situation.

This CL fixes the way we prevent from posting method enter/exit events during
the process of deoptimization/undeoptimization. We now explicitly set a flag
indicating if deoptimization is enabled (by the debugger).

Also removes unused field in InstallStackVisitor class and remove debugger as
listener before disabling deoptimization to ensure it does not receive any
event when disconnecting.

Change-Id: I49a2ae43e86cf29094f4b462bfa754d7740d3e97