Summary:
Previously, annotating something ThreadSafe meant "check that it is safe to run all of this procedure's methods in parallel with each other" (including self-parallelization).
This makes sense, but it means that if the user writes no annotations, we do no checking.
I'm moving toward a model of inferring when an access might happen on a thread that can run concurrently with other threads, then automatically checking that it is thread-safe w.r.t to all other accesses to the same memory (on or off the current thread thread).
This will let us report even when there are no `ThreadSafe` annotations.
Any method that is known to run on a new thread (e.g., `Runnable.run`) will be modeled as running on a thread that can run in parallel with other threads, and so will any method that is `synchronized` or acquires a lock.
In this setup, adding `ThreadSafe` to a method just means: "assume that the current method can run in parallel with any thread, including another thread that includes a different invocation of the same method (a self race) unless you see evidence to the contrary" (e.g., calling `assertMainThread` or annotating with `UiThread`).
The key step in this diff is changing the threads domain to abstract *what threads the current thread may run in parallel with* rather than *what the current thread* is. This makes things much simpler.
Reviewed By: jberdine
Differential Revision: D5895242
fbshipit-source-id: 2e23d1e
Summary: Handling the utility functions for asserting that we're on background thread.
Reviewed By: jberdine
Differential Revision: D5863435
fbshipit-source-id: 3ad95b5
Summary:
Previously, we just tracked a boolean representing whether we were possibly on the main thread (true) or definitely not on the main thread (false).
In order to start supporting `Thread.start`, `Runnable.run`, etc., we'll need something more expressive.
This diff introduces a lattice:
```
Any
/ \
Main Background
\ /
Unknown
```
as the new threads domain. The initial value is `Unknown`, and we introduce `Main` in situations where we would have introduced `true` before.
This (mostly) preserves behavior: the main difference is that before code like
```
if (*) {
assertMainThread()
} else {
x.f = ...
}
```
would have recorded that the access to `x.f` was on the main thread, whereas now we'll say that it's on an unknown thread.
Reviewed By: peterogithub
Differential Revision: D5860256
fbshipit-source-id: efee330
Summary: Using Conjunction for thread join has known false negatives. Finer grained recording of threading information fixes this.
Reviewed By: sblackshear
Differential Revision: D5111161
fbshipit-source-id: aab483c
Summary:
There are false positives in the current analysis due to the
use of conjunction in the treatment of threaded. Changing conjunction to disjunction
removes these false positives. Some new false negatives arise, but all the old tests pass.
This is a stopgap towards a better solution being planned.
Reviewed By: sblackshear
Differential Revision: D4883280
fbshipit-source-id: c2a7e6e
Summary:
This was the one type of races we were not yet reporting (besides ones that use the wrong synchronization :)).
Wrote new utility function to aggregate all accesses by the memory they access.
This makes it easy to say which accesses we should report and what their conflicts are.
Eventually, we can simplify the reporting of other kinds of unsafe accesses using this structure.
Reviewed By: peterogithub
Differential Revision: D4770542
fbshipit-source-id: 96d948e
Sam Blackshear
Peter O'Hearn