From 810f7414427277dfa86d3821aef9ba584564ef64 Mon Sep 17 00:00:00 2001
From: Max Wash <mbswash@gmail.com>
Date: Sun, 19 Jul 2026 13:31:22 +0100
Subject: [PATCH] libc: pthread: implement mutexes

---
 lib/libc/pthread/include/pthread.h            |  8 ++++++-
 lib/libc/pthread/mutex/pthread_mutex_lock.c   | 24 +++++++++++++++++++
 .../pthread/mutex/pthread_mutex_trylock.c     | 18 ++++++++++++++
 lib/libc/pthread/mutex/pthread_mutex_unlock.c |  8 +++++++
 4 files changed, 57 insertions(+), 1 deletion(-)
 create mode 100644 lib/libc/pthread/mutex/pthread_mutex_lock.c
 create mode 100644 lib/libc/pthread/mutex/pthread_mutex_trylock.c
 create mode 100644 lib/libc/pthread/mutex/pthread_mutex_unlock.c

diff --git a/lib/libc/pthread/include/pthread.h b/lib/libc/pthread/include/pthread.h
index f029886..dcf4bef 100644
--- a/lib/libc/pthread/include/pthread.h
+++ b/lib/libc/pthread/include/pthread.h
@@ -3,7 +3,9 @@
 
 #include <magenta/types.h>
 
-#define __PTHREAD_ATTR_SIZE__ 32
+#define __PTHREAD_ATTR_SIZE__     32
+
+#define PTHREAD_MUTEX_INITIALIZER ((pthread_mutex_t) {.__v = 0})
 
 typedef struct __pthread *pthread_t;
 
@@ -28,4 +30,8 @@ extern int pthread_join(pthread_t thread, void **retval);
 extern int pthread_detach(pthread_t thread);
 extern void pthread_exit(void *retval);
 
+extern int pthread_mutex_lock(pthread_mutex_t *mut);
+extern int pthread_mutex_trylock(pthread_mutex_t *mut);
+extern int pthread_mutex_unlock(pthread_mutex_t *mut);
+
 #endif
diff --git a/lib/libc/pthread/mutex/pthread_mutex_lock.c b/lib/libc/pthread/mutex/pthread_mutex_lock.c
new file mode 100644
index 0000000..97c0166
--- /dev/null
+++ b/lib/libc/pthread/mutex/pthread_mutex_lock.c
@@ -0,0 +1,24 @@
+#include <errno.h>
+#include <magenta/futex.h>
+#include <pthread.h>
+
+int pthread_mutex_lock(pthread_mutex_t *mut)
+{
+	kern_futex_t expected = 0;
+	while (1) {
+		expected = 0;
+		if (__atomic_compare_exchange_n(
+			    &mut->__v,
+			    &expected,
+			    1,
+			    0,
+			    __ATOMIC_ACQUIRE,
+			    __ATOMIC_ACQUIRE)) {
+			return 0;
+		}
+
+		futex_wait(&mut->__v, 1, FUTEX_PRIVATE);
+	}
+
+	return __set_errno(EAGAIN);
+}
diff --git a/lib/libc/pthread/mutex/pthread_mutex_trylock.c b/lib/libc/pthread/mutex/pthread_mutex_trylock.c
new file mode 100644
index 0000000..d3d360e
--- /dev/null
+++ b/lib/libc/pthread/mutex/pthread_mutex_trylock.c
@@ -0,0 +1,18 @@
+#include <errno.h>
+#include <pthread.h>
+
+int pthread_mutex_trylock(pthread_mutex_t *mut)
+{
+	kern_futex_t expected = 0;
+	if (__atomic_compare_exchange_n(
+		    &mut->__v,
+		    &expected,
+		    1,
+		    0,
+		    __ATOMIC_ACQUIRE,
+		    __ATOMIC_ACQUIRE)) {
+		return 0;
+	}
+
+	return __set_errno(EBUSY);
+}
diff --git a/lib/libc/pthread/mutex/pthread_mutex_unlock.c b/lib/libc/pthread/mutex/pthread_mutex_unlock.c
new file mode 100644
index 0000000..6fea185
--- /dev/null
+++ b/lib/libc/pthread/mutex/pthread_mutex_unlock.c
@@ -0,0 +1,8 @@
+#include <magenta/futex.h>
+#include <pthread.h>
+
+int pthread_mutex_unlock(pthread_mutex_t *mut)
+{
+	mut->__v = 0;
+	futex_wake(&mut->__v, 1, FUTEX_PRIVATE);
+}