binder: Use wake up hint for synchronous transactions.

Use wake_up_interruptible_sync() to hint to the scheduler binder
transactions are synchronous wakeups. Disable preemption while waking
to avoid ping-ponging on the binder lock.

Signed-off-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Omprakash Dhyade <odhyade@codeaurora.org>
Cc: stable <stable@vger.kernel.org> # 4.4+
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 9393924ae8e8..f7665c31feca 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2200,8 +2200,12 @@ static void binder_transaction(struct binder_proc *proc,
         list_add_tail(&t->work.entry, target_list);
         tcomplete->type = BINDER_WORK_TRANSACTION_COMPLETE;
         list_add_tail(&tcomplete->entry, &thread->todo);
-        if (target_wait)
-                wake_up_interruptible(target_wait);
+        if (target_wait) {
+                if (reply || !(t->flags & TF_ONE_WAY))
+                        wake_up_interruptible_sync(target_wait);
+                else
+                        wake_up_interruptible(target_wait);
+        }
         return;
 
 err_translate_failed: