Merge branch 'mutex-fork-test' into 'master'

Add fork inside thread test

See merge request redox-os/relibc!886

tests/pthread/thread_fork.c

@@ -0,0 +1,51 @@
+/// test fork inside thread
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <pthread.h>
+#include <sys/wait.h>
+
+#include "test_helpers.h"
+
+#define NUM_THREADS 4
+#define ITERATIONS 3
+
+
+void* thread_func(void* arg) {
+    long tid = (long)arg;
+
+    for (int i = 0; i < ITERATIONS; i++) {
+        printf("thread %ld loop %i\n", tid, i);
+
+        pid_t pid = fork();
+        ERROR_IF(fork, pid, < 0);
+
+        if (pid == 0) {
+            _exit(0);
+        } else {
+            waitpid(pid, NULL, 0);
+        }
+
+        usleep(1000); 
+    }
+
+    return NULL;
+}
+
+int main() {
+    pthread_t threads[NUM_THREADS];
+    int status;
+
+    for (long i = 0; i < NUM_THREADS; i++) {
+        status = pthread_create(&threads[i], NULL, thread_func, (void*)i);
+        ERROR_IF(pthread_create, status, != 0);
+    }
+
+    printf("joining threads\n");
+    for (int i = 0; i < NUM_THREADS; i++) {
+        pthread_join(threads[i], NULL);
+    }
+
+    return 0;
+}