unix: Add recursive mutex support.

Allows refactoring the existing thread_mutex atomic section support to use
the new recursive mutex type.

This work was funded through GitHub Sponsors.

Signed-off-by: Angus Gratton <angus@redyak.com.au>

Author: projectgus

ports/unix/mpthreadport.c

@@ -65,7 +65,7 @@ static pthread_key_t tls_key;
 // The mutex is used for any code in this port that needs to be thread safe.
 // Specifically for thread management, access to the linked list is one example.
 // But also, e.g. scheduler state.
-static pthread_mutex_t thread_mutex;
+static mp_thread_recursive_mutex_t thread_mutex;
 static mp_thread_t *thread;
 
 // this is used to synchronise the signal handler of the thread
@@ -78,11 +78,11 @@ static sem_t thread_signal_done;
 #endif
 
 void mp_thread_unix_begin_atomic_section(void) {
-    pthread_mutex_lock(&thread_mutex);
+    mp_thread_recursive_mutex_lock(&thread_mutex, true);
 }
 
 void mp_thread_unix_end_atomic_section(void) {
-    pthread_mutex_unlock(&thread_mutex);
+    mp_thread_recursive_mutex_unlock(&thread_mutex);
 }
 
 // this signal handler is used to scan the regs and stack of a thread
@@ -113,10 +113,7 @@ void mp_thread_init(void) {
 
     // Needs to be a recursive mutex to emulate the behavior of
     // BEGIN_ATOMIC_SECTION on bare metal.
-    pthread_mutexattr_t thread_mutex_attr;
-    pthread_mutexattr_init(&thread_mutex_attr);
-    pthread_mutexattr_settype(&thread_mutex_attr, PTHREAD_MUTEX_RECURSIVE);
-    pthread_mutex_init(&thread_mutex, &thread_mutex_attr);
+    mp_thread_recursive_mutex_init(&thread_mutex);
 
     // create first entry in linked list of all threads
     thread = malloc(sizeof(mp_thread_t));
@@ -321,6 +318,26 @@ void mp_thread_mutex_unlock(mp_thread_mutex_t *mutex) {
     // TODO check return value
 }
 
+#if MICROPY_PY_THREAD_RECURSIVE_MUTEX
+
+void mp_thread_recursive_mutex_init(mp_thread_recursive_mutex_t *mutex) {
+    pthread_mutexattr_t attr;
+    pthread_mutexattr_init(&attr);
+    pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
+    pthread_mutex_init(mutex, &attr);
+    pthread_mutexattr_destroy(&attr);
+}
+
+int mp_thread_recursive_mutex_lock(mp_thread_recursive_mutex_t *mutex, int wait) {
+    return mp_thread_mutex_lock(mutex, wait);
+}
+
+void mp_thread_recursive_mutex_unlock(mp_thread_recursive_mutex_t *mutex) {
+    mp_thread_mutex_unlock(mutex);
+}
+
+#endif // MICROPY_PY_THREAD_RECURSIVE_MUTEX
+
 #endif // MICROPY_PY_THREAD
 
 // this is used even when MICROPY_PY_THREAD is disabled

ports/unix/mpthreadport.h

@@ -28,6 +28,7 @@
 #include <stdbool.h>
 
 typedef pthread_mutex_t mp_thread_mutex_t;
+typedef pthread_mutex_t mp_thread_recursive_mutex_t;
 
 void mp_thread_init(void);
 void mp_thread_deinit(void);