Android Native Code Fork() Has Issues With Ipc/binder

I have an Android native Server app compiled as Platform privileged module that forks itself. This module also uses Android services, like SurfaceFlinger. I need to fork to have on

Solution 1:

You can't create a new Binder process this way.

The problem is that fork() only clones the current thread, not all threads. In the new process, the Binder IPC code will expect the Binder helper threads to be running, but none of them will be. You need to fork() and then exec().

The zygote process avoids this issue by having only one thread running when fork() is called. It deliberately defers initialization of the Binder code to the child process. (In the current implementation, it actually has a couple of threads running in Dalvik, but the internal fork handling stops and restarts those threads on every fork).

Solution 2:

fadden is right, fork() cannot be used to create a new process that uses Android APIs reliably. The best you can do with it is exec() to run a standalone command-line program, everything else is likely to not work as you expect.

However, the platform supports sandboxed processes, in the form of isolated service processes. See http://developer.android.com/guide/topics/manifest/service-element.html#isolated for more details. In essence, this runs your service in a special process under a random UID that has no permissions.

For the record, this is what Chrome on Android uses to isolate 'tabs' into sandboxed 'renderer processes'.