BACKPORT: FROMGIT: binder: BINDER_FREEZE ioctl

Frozen tasks can't process binder transactions, so a way is required to
inform transmitting ends of communication failures due to the frozen
state of their receiving counterparts. Additionally, races are possible
between transitions to frozen state and binder transactions enqueued to
a specific process.

Implement BINDER_FREEZE ioctl for user space to inform the binder driver
about the intention to freeze or unfreeze a process. When the ioctl is
called, block the caller until any pending binder transactions toward
the target process are flushed. Return an error to transactions to
processes marked as frozen.

Bug: 180989544
(cherry picked from commit 15949c3cdd97bccdcd45c0c0f6c31058520b6494
 git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git

 char-misc-testing)
Co-developed-by: Todd Kjos <tkjos@google.com>
Acked-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Marco Ballesio <balejs@google.com>
Signed-off-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Li Li <dualli@google.com>
Link: https://lore.kernel.org/r/20210316011630.1121213-2-dualli@chromium.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Change-Id: Ia1b5951cd99eeb98b59e06c3e27d59062dc725f6