When passing a refnum across the language barrier there is a small
window where a proxy object itself can be garbage collected, its
reference count go to 0 and the object be gone when the refnum
is dereferenced on the other side.
In Go the proxy object is pinned with runtime.KeepAlive. This CL
implements the same mechanism in Java by passing the proxy object to
native code, ensuring the Java GC can't reclaim it during the call.
Change-Id: I23824439012eb00f90d729f59d4846999f24f01f
Reviewed-on: https://go-review.googlesource.com/107095
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Android runs a finalizer watchdog that tracks the running time of
finalizers and throws an exception if any runs too long. Our
finalizers do very little work and as such are not affected by the
timeout. However, there has been reports, for example:
https://stackoverflow.com/questions/24021609/how-to-handle-java-util-concurrent-timeoutexception-android-os-binderproxy-fin
that the watchdog does not take into account periods where the device
goes to sleep in the middle of a finalizer run. So if a given app runs
in the background, the Java GC starts a finalizer and the device goes
to sleep before it returns, an exception will crash the app if the sleep
period extends the watchdog timeout.
The problem might be fixed on some newer version of Android, but the
problem is reported for as late as Android 6.
The suggested workaround is to use PhantomReferences and run a
background thread that take dead references off a ReferenceQueue and
perform cleanup.
This CL builds on the previous CL and splits up the Ref class so Refs
only reference counts Java objects, while a new class GoRef tracks Go
references. The Go references are wrapped in PhantomReferences that in
turn appear on a GoRefQueue to be cleaned up by a background (daemon)
Thread.
Change-Id: I04e3296b851999c612d3baf6a593cc044c2c5bdd
Reviewed-on: https://go-review.googlesource.com/106876
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Today, the Seq.Ref class has two purposes. For Java references,
Ref contains the refnum, a reference to the Java object and a
reference count. For Go references, Ref contains the refnum and
its finalizer makes sure to decrement the reference count on the Go
side.
The next CL will replace the use of finalizers with an explicit
ReferenceQueue of Go references, and the Ref class will no longer
be used for Go refences. To prepare for that, this CL pulls up the
construction of Go referencing Ref instances into the Seq.trackGoRef
function.
Change-Id: I9eefe238cd3fd1b661b2af11d331a2f61e31303b
Reviewed-on: https://go-review.googlesource.com/106875
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
Convert Go documentation to JavaDoc tags (/** ... */).
Since the .aar file format doesn't support source files, gomobile
will create a package-sources.jar along with the main package.aar.
For Objective-C, JavaDoc-style comments seems to work as well,
judging by manual inspection of Xcode quick help.
Change-Id: I47fe5b6804681d459a873be37a44610d392166ef
Reviewed-on: https://go-review.googlesource.com/52330
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
