Thread ID zero for androidSetThreadSchedulingGroup

Already implemented by androidSetThreadPriority but not documented

Change-Id: I85302b17092952065f3f3a4214d8d8abdd465dbd

2 files changed, 6 insertions, 2 deletions

diff --git a/include/utils/threads.h b/include/utils/threads.h
index 0bd69cf377..41f67e4058 100644
--- a/include/utils/threads.h
+++ b/include/utils/threads.h
@@ -133,13 +133,13 @@ extern pid_t androidGetTid();
 // Change the scheduling group of a particular thread.  The group
 // should be one of the ANDROID_TGROUP constants.  Returns BAD_VALUE if
 // grp is out of range, else another non-zero value with errno set if
-// the operation failed.
+// the operation failed.  Thread ID zero means current thread.
 extern int androidSetThreadSchedulingGroup(pid_t tid, int grp);
 
 // Change the priority AND scheduling group of a particular thread.  The priority
 // should be one of the ANDROID_PRIORITY constants.  Returns INVALID_OPERATION
 // if the priority set failed, else another value if just the group set failed;
-// in either case errno is set.
+// in either case errno is set.  Thread ID zero means current thread.
 extern int androidSetThreadPriority(pid_t tid, int prio);
 
 #ifdef __cplusplus
diff --git a/libs/utils/Threads.cpp b/libs/utils/Threads.cpp
index 15bb1d2262..71352a864f 100644
--- a/libs/utils/Threads.cpp
+++ b/libs/utils/Threads.cpp
@@ -316,6 +316,10 @@ int androidSetThreadSchedulingGroup(pid_t tid, int grp)
 #if defined(HAVE_PTHREADS)
     pthread_once(&gDoSchedulingGroupOnce, checkDoSchedulingGroup);
     if (gDoSchedulingGroup) {
+        // set_sched_policy does not support tid == 0
+        if (tid == 0) {
+            tid = androidGetTid();
+        }
         if (set_sched_policy(tid, (grp == ANDROID_TGROUP_BG_NONINTERACT) ?
                                           SP_BACKGROUND : SP_FOREGROUND)) {
             return PERMISSION_DENIED;