barrier: More efficient impl, maybe

nx/include/switch/kernel/barrier.h

@@ -5,15 +5,15 @@
  * @copyright libnx Authors
  */
 #pragma once
-#include "semaphore.h"
+#include "mutex.h"
+#include "condvar.h"
 
 /// Barrier structure.
 typedef struct Barrier {
-    u64 count;             ///< Number of threads to reach the barrier.
-    u64 thread_total;      ///< Number of threads to wait on.
-    Semaphore throttle;    ///< Semaphore to make sure threads release to scheduler one at a time.
-    Semaphore lock;        ///< Semaphore to lock barrier to prevent multiple operations by threads at once.
-    Semaphore thread_wait; ///< Semaphore to force a thread to wait if count < thread_total.
+    u64 count;  ///< Number of threads to reach the barrier.
+    u64 total;  ///< Number of threads to wait on.
+    Mutex mutex;
+    CondVar condvar;
 } Barrier;
 
 /**

nx/source/kernel/barrier.c

@@ -1,29 +1,22 @@
 #include "kernel/barrier.h"
 
-void barrierInit(Barrier *b, u64 thread_count) {
+void barrierInit(Barrier *b, u64 total) {
     b->count = 0;
-    b->thread_total = thread_count;
-    semaphoreInit(&b->throttle, 0);
-    semaphoreInit(&b->lock, 1);
-    semaphoreInit(&b->thread_wait, 0);
+    b->total = total - 1;
+    mutexInit(&b->mutex);
+    condvarInit(&b->condvar);
 }
 
 void barrierWait(Barrier *b) {
-    semaphoreWait(&b->lock);
-    if(b->count < b->thread_total) {
-        b->count++;
+    mutexLock(&b->mutex);
+
+    if (b->count++ == b->total) {
+      b->count = 0;
+      condvarWake(&b->condvar, b->total);
     }
-    if(b->count < b->thread_total) {
-        semaphoreSignal(&b->lock);
-        semaphoreWait(&b->thread_wait);
-        semaphoreSignal(&b->throttle);
-    }
-    else if(b->count == b->thread_total) {
-        for(int i = 0; i < b->thread_total-1; i++) {
-            semaphoreSignal(&b->thread_wait);
-            semaphoreWait(&b->throttle);
-        }
-        b->count = 0;
-        semaphoreSignal(&b->lock);
+    else {
+       condvarWait(&b->condvar, &b->mutex);
     }
+
+    mutexUnlock(&b->mutex);
 }