Add example with multiple threads creation

samples/wasi-threads/wasm-apps/CMakeLists.txt

@@ -34,3 +34,4 @@ endfunction ()
 
 compile_sample(no_pthread.c)
 compile_sample(exception_propagation.c)
+compile_sample(multiple_threads.c)

samples/wasi-threads/wasm-apps/multiple_threads.c

@@ -0,0 +1,84 @@
+/*
+ * Copyright (C) 2022 Amazon.com Inc. or its affiliates. All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+#ifndef __wasi__
+#error This example only compiles to WASM/WASI target
+#endif
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <assert.h>
+#include <wasi/api.h>
+#include <stdbool.h>
+
+#define MAX_NUM_THREADS 4 // Default maximum number of threads for iwasm
+static const int64_t SECOND = 1000 * 1000 * 1000;
+
+typedef struct {
+    int th_ready;
+    int th_done;
+} shared_t;
+
+__attribute__((export_name("wasi_thread_start"))) void
+wasi_thread_start(int thread_id, int *start_arg)
+{
+    shared_t *data = (shared_t *)start_arg;
+
+    if (__builtin_wasm_memory_atomic_wait32(&data->th_ready, 0, SECOND) == 2)
+        assert(false && "Wait operation in thread failed");
+
+    data->th_done = 1;
+    __builtin_wasm_memory_atomic_notify(&data->th_done, 1);
+}
+
+int
+main(int argc, char **argv)
+{
+    int thread_ids[MAX_NUM_THREADS];
+    shared_t data[MAX_NUM_THREADS] = { 0 };
+
+    for (int i = 0; i < MAX_NUM_THREADS; i++) {
+        thread_ids[i] = __wasi_thread_spawn(&data[i]);
+        printf("Created thread with id = %d\n", thread_ids[i]);
+        assert(thread_ids[i] >= 0 && "Thread ids must be >= 0");
+
+        bool is_id_already_existing = false;
+        for (int j = 0; j < i; j++) {
+            if (thread_ids[i] == thread_ids[j])
+                is_id_already_existing = true;
+        }
+        assert(!is_id_already_existing && "Thread ids must be unique");
+    }
+
+    printf("Try to create additional thread after limit reached\n");
+    shared_t data_fail = { 0 };
+    int thread_id = __wasi_thread_spawn(&data_fail);
+    assert(thread_id < 0 && "Thread creation must fail");
+
+    // Unlock first-created thread
+    data[0].th_ready = 1;
+    __builtin_wasm_memory_atomic_notify(&data[0].th_ready, 1);
+    // And wait for it to return
+    if (__builtin_wasm_memory_atomic_wait32(&data[0].th_done, 0, SECOND) == 2)
+        assert(false && "Wait operation in main thread failed");
+
+    printf("Try to create additional thread after previous was released\n");
+    shared_t data_succeed = { 0 };
+    thread_id = __wasi_thread_spawn(&data_succeed);
+    assert(thread_id >= 0 && "Thread creation must succeed");
+
+    printf("Created thread with id = %d\n", thread_id);
+    assert(thread_id == thread_ids[0]
+           && "New thread must reuse previously-released identifier");
+
+    // Unlock all running threads
+    data_succeed.th_ready = 1;
+    __builtin_wasm_memory_atomic_notify(&data_succeed.th_ready, 1);
+    for (int i = 1; i < MAX_NUM_THREADS; i++) {
+        data[i].th_ready = 1;
+        __builtin_wasm_memory_atomic_notify(&data[i].th_ready, 1);
+    }
+
+    return EXIT_SUCCESS;
+}