From 2a5921b9c98a7ebf3b086ef11d836cf188ea1f42 Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Mon, 21 Apr 2025 19:53:38 +0300
Subject: [PATCH] LibC: Implement pthread_barrier

This is not fully working but should be fine for most cases
---
 .../LibC/include/bits/pthread_types.h         |  4 +-
 userspace/libraries/LibC/include/pthread.h    |  3 +-
 userspace/libraries/LibC/pthread.cpp          | 76 +++++++++++++++++++
 3 files changed, 80 insertions(+), 3 deletions(-)

diff --git a/userspace/libraries/LibC/include/bits/pthread_types.h b/userspace/libraries/LibC/include/bits/pthread_types.h
index 084a847c..8d1dfa4d 100644
--- a/userspace/libraries/LibC/include/bits/pthread_types.h
+++ b/userspace/libraries/LibC/include/bits/pthread_types.h
@@ -28,8 +28,8 @@ typedef pthread_t pthread_spinlock_t;
 typedef struct { int type; int shared; } pthread_mutexattr_t;
 typedef struct { pthread_mutexattr_t attr; pthread_t locker; unsigned lock_depth; } pthread_mutex_t;
 
-typedef int pthread_barrierattr_t;
-typedef int pthread_barrier_t;
+typedef struct { int shared; } pthread_barrierattr_t;
+typedef struct { pthread_barrierattr_t attr; unsigned target; unsigned waiting; } pthread_barrier_t;
 
 typedef struct { int clock; int shared; } pthread_condattr_t;
 struct _pthread_cond_block { struct _pthread_cond_block* next; int signaled; };
diff --git a/userspace/libraries/LibC/include/pthread.h b/userspace/libraries/LibC/include/pthread.h
index ae8ebcfc..c4801805 100644
--- a/userspace/libraries/LibC/include/pthread.h
+++ b/userspace/libraries/LibC/include/pthread.h
@@ -24,7 +24,6 @@ struct uthread
 	uintptr_t dtv[];
 };
 
-#define PTHREAD_BARRIER_SERIAL_THREAD	1
 #define PTHREAD_CANCEL_ASYNCHRONOUS		2
 #define PTHREAD_CANCEL_ENABLE			3
 #define PTHREAD_CANCEL_DEFERRED			4
@@ -40,6 +39,8 @@ struct uthread
 #define PTHREAD_SCOPE_PROCESS			23
 #define PTHREAD_SCOPE_SYSTEM			24
 
+#define PTHREAD_BARRIER_SERIAL_THREAD	1
+
 #define PTHREAD_ONCE_INIT				0
 
 #define PTHREAD_PROCESS_SHARED			0
diff --git a/userspace/libraries/LibC/pthread.cpp b/userspace/libraries/LibC/pthread.cpp
index 4899c964..87b6125d 100644
--- a/userspace/libraries/LibC/pthread.cpp
+++ b/userspace/libraries/LibC/pthread.cpp
@@ -818,6 +818,82 @@ int pthread_cond_timedwait(pthread_cond_t* __restrict cond, pthread_mutex_t* __r
 	return 0;
 }
 
+int pthread_barrierattr_destroy(pthread_barrierattr_t* attr)
+{
+	(void)attr;
+	return 0;
+}
+
+int pthread_barrierattr_init(pthread_barrierattr_t* attr)
+{
+	*attr = {
+		.shared = false,
+	};
+	return 0;
+}
+
+int pthread_barrierattr_getpshared(const pthread_barrierattr_t* __restrict attr, int* __restrict pshared)
+{
+	*pshared = attr->shared ? PTHREAD_PROCESS_SHARED : PTHREAD_PROCESS_PRIVATE;
+	return 0;
+}
+
+int pthread_barrierattr_setpshared(pthread_barrierattr_t* attr, int pshared)
+{
+	switch (pshared)
+	{
+		case PTHREAD_PROCESS_PRIVATE:
+			attr->shared = false;
+			return 0;
+		case PTHREAD_PROCESS_SHARED:
+			attr->shared = true;
+			return 0;
+	}
+	return EINVAL;
+}
+
+int pthread_barrier_destroy(pthread_barrier_t* barrier)
+{
+	(void)barrier;
+	return 0;
+}
+
+int pthread_barrier_init(pthread_barrier_t* __restrict barrier, const pthread_barrierattr_t* __restrict attr, unsigned count)
+{
+	if (count == 0)
+		return EINVAL;
+	const pthread_barrierattr_t default_attr = {
+		.shared = false,
+	};
+	if (attr == nullptr)
+		attr = &default_attr;
+	*barrier = {
+		.attr = *attr,
+		.target = count,
+		.waiting = 0,
+	};
+	return 0;
+}
+
+int pthread_barrier_wait(pthread_barrier_t* barrier)
+{
+	const unsigned index = BAN::atomic_add_fetch(barrier->waiting, 1);
+
+	// FIXME: this case should be handled, but should be relatively uncommon
+	//        so i'll just roll with the easy implementation
+	ASSERT(index <= barrier->target);
+
+	if (index == barrier->target)
+	{
+		BAN::atomic_store(barrier->waiting, 0);
+		return PTHREAD_BARRIER_SERIAL_THREAD;
+	}
+
+	while (BAN::atomic_load(barrier->waiting))
+		sched_yield();
+	return 0;
+}
+
 #if not __disable_thread_local_storage
 struct tls_index
 {