Revert^2 "Add spin loop to mutex, overhaul monitor"
This reverts commit d56f7d1086b16f32c0771a41a4afb376b5fd3076.
Reason for revert: PS2 fixes the problems I identified.
PS1 is straight revert^2 of, and thus identical to aosp/1111800.
PS2 in addition:
- Reduces the size of the test, when not modified to run as benchmark.
- Disables the test in slow-running configurations, which timed out.
- Stops using the mutex recursion count, and instead reintroduces
one at the monitor level. The plan is to eliminate the one in mutex
in a future CL.
- Avoids modifying various monitor fields in suspended state.
MonitorInfo, deflation, etc., may look at the state of a suspended
thread and expect not to race. I don't think the original code had
this completely correct either, but PS1 made it worse.
- Documents some aspects of the code that confused me at times.
- Avoids dereferencing the monitor owner Thread* unless it holds the
thread list lock, and thus knows that the thread won't go away.
- Stores a Thread* instead of a thread_id with the monitor owner method
and dex pc information used for debugging. This is required to avoid
extra thread list lock acquisitions, since we need to dereference the
owner to get the thread id.
- Makes the thread list Contains method public, again in order to
support the above. (This ignores C/C++ restrictions on dangling
pointer use. We already rely on violating those elsewhere, and
the committees are trying to get their story straight about this.)
- Causes the spin loop to give up immediately if the process is
shutting down. This gets us to an actual idle state sooner in that
case, and should hopefully mitigate the shutdown issues somewhat.
(We tried not spinnning in "suspended" state, but that reintroduced
some performance issues.)
- Makes runtime shutdown code more defensive. Clear fields pointing to
deallocated objects. Always wait for quiescence AFTER all threads
are suspended.
- Consistently checks for a runtime that's shutting down or missing
after waking up from a futex wait, thus avoiding touching deallocated
memory. I believe this was the cause of b/121302864, which PS1
managed to aggravate.
- SleepForever() was a very light sleeper, waking up once a second.
Fix that, so the daemon threads we leak on runtime shutdown cost
us less.
- Remove a data race from the "was the runtime deleted" logic.
Bug: 140590186
Bug: 121302864
Test: Build and boot AOSP.
Test: art/test/testrunner/testrunner.py --host -b -t 1932-monitor-events-misc
Test: art/test/testrunner/testrunner.py --host -b -t 132-daemon-locks-shutdown
Test: art/test/testrunner/testrunner.py --host -b -t 004-ThreadStress
Change-Id: I6667c61beed2ba68c84cd4c0821fb8e21e188bbc
17 files changed