Caching scheduling policy and priority in userland, a critical but baddly

written application is frequently changing thread priority for SCHED_OTHER
policy.

1 files changed, 22 insertions, 8 deletions

diff --git a/lib/libthr/thread/thr_setprio.c b/lib/libthr/thread/thr_setprio.c
index 03ac39c..78769d1 100644
--- a/lib/libthr/thread/thr_setprio.c
+++ b/lib/libthr/thread/thr_setprio.c
@@ -50,20 +50,34 @@ _pthread_setprio(pthread_t pthread, int prio)
 	param.sched_priority = prio;
 	if (pthread == curthread) {
 		THR_LOCK(curthread);
-		ret = thr_setschedparam(curthread->tid, &param, sizeof(param));
-		if (ret == -1)
-			ret = errno;
-		else
+		if (curthread->attr.sched_policy == SCHED_OTHER ||
+		    curthread->attr.prio == prio) {
 			curthread->attr.prio = prio;
+			ret = 0;
+		} else {
+			ret = thr_setschedparam(curthread->tid,
+				 &param, sizeof(param));
+			if (ret == -1)
+				ret = errno;
+			else 
+				curthread->attr.prio = prio;
+		}
 		THR_UNLOCK(curthread);
 	} else if ((ret = _thr_ref_add(curthread, pthread, /*include dead*/0))
 		== 0) {
 		THR_THREAD_LOCK(curthread, pthread);
-		ret = thr_setschedparam(pthread->tid, &param, sizeof(param));
-		if (ret == -1)
-			ret = errno;
-		else
+		if (pthread->attr.sched_policy == SCHED_OTHER ||
+		    pthread->attr.prio == prio) {
 			pthread->attr.prio = prio;
+			ret = 0;
+		} else {
+			ret = thr_setschedparam(pthread->tid, &param,
+				sizeof(param));
+			if (ret == -1)
+				ret = errno;
+			else
+				pthread->attr.prio = prio;
+		}
 		THR_THREAD_UNLOCK(curthread, pthread);
 		_thr_ref_delete(curthread, pthread);
 	}