From 092efbfe219063c7854bf6298216eaf828871d73 Mon Sep 17 00:00:00 2001
From: Wenyong Huang <wenyong.huang@intel.com>
Date: Mon, 17 Jan 2022 17:09:04 +0800
Subject: [PATCH] Fix thread manager issues (#962)

Fix the issue that joining a detached thread might result in joining hang,
resolve the issue by adding wait_count for a thread's exec_env to indicate
whether a thread needs to detach itself or not when it exits.

And add checks for the input exec_env for cluster's join/detach/cancel thread.
---
 core/iwasm/common/wasm_exec_env.h             |  2 +
 .../libraries/thread-mgr/thread_manager.c     | 65 ++++++++++++++++++-
 .../libraries/thread-mgr/thread_manager.h     |  1 +
 3 files changed, 66 insertions(+), 2 deletions(-)

diff --git a/core/iwasm/common/wasm_exec_env.h b/core/iwasm/common/wasm_exec_env.h
index ea2fafd6..86ad1c3e 100644
--- a/core/iwasm/common/wasm_exec_env.h
+++ b/core/iwasm/common/wasm_exec_env.h
@@ -98,6 +98,8 @@ typedef struct WASMExecEnv {
     /* used to support debugger */
     korp_mutex wait_lock;
     korp_cond wait_cond;
+    /* the count of threads which are joining current thread */
+    uint32 wait_count;
 #endif
 
 #if WASM_ENABLE_DEBUG_INTERP != 0
diff --git a/core/iwasm/libraries/thread-mgr/thread_manager.c b/core/iwasm/libraries/thread-mgr/thread_manager.c
index f6987c0c..8db457c2 100644
--- a/core/iwasm/libraries/thread-mgr/thread_manager.c
+++ b/core/iwasm/libraries/thread-mgr/thread_manager.c
@@ -625,16 +625,69 @@ wasm_cluster_set_debug_inst(WASMCluster *cluster, WASMDebugInstance *inst)
 
 #endif /* end of WASM_ENABLE_DEBUG_INTERP */
 
+/* Check whether the exec_env is in one of all clusters, the caller
+   should add lock to the cluster list before calling us */
+static bool
+clusters_have_exec_env(WASMExecEnv *exec_env)
+{
+    WASMCluster *cluster = bh_list_first_elem(cluster_list);
+    WASMExecEnv *node;
+
+    while (cluster) {
+        node = bh_list_first_elem(&cluster->exec_env_list);
+
+        while (node) {
+            if (node == exec_env) {
+                bh_assert(exec_env->cluster == cluster);
+                return true;
+            }
+            node = bh_list_elem_next(node);
+        }
+
+        cluster = bh_list_elem_next(cluster);
+    }
+
+    return false;
+}
+
 int32
 wasm_cluster_join_thread(WASMExecEnv *exec_env, void **ret_val)
 {
-    return os_thread_join(exec_env->handle, ret_val);
+    korp_tid handle;
+
+    os_mutex_lock(&cluster_list_lock);
+    if (!clusters_have_exec_env(exec_env)) {
+        /* Invalid thread or the thread has exited */
+        if (ret_val)
+            *ret_val = NULL;
+        os_mutex_unlock(&cluster_list_lock);
+        return 0;
+    }
+    exec_env->wait_count++;
+    handle = exec_env->handle;
+    os_mutex_unlock(&cluster_list_lock);
+    return os_thread_join(handle, ret_val);
 }
 
 int32
 wasm_cluster_detach_thread(WASMExecEnv *exec_env)
 {
-    return os_thread_detach(exec_env->handle);
+    int32 ret = 0;
+
+    os_mutex_lock(&cluster_list_lock);
+    if (!clusters_have_exec_env(exec_env)) {
+        /* Invalid thread or the thread has exited */
+        os_mutex_unlock(&cluster_list_lock);
+        return 0;
+    }
+    if (exec_env->wait_count == 0) {
+        /* Only detach current thread when there is no other thread
+           joining it, otherwise let the system resources for the
+           thread be released after joining */
+        ret = os_thread_detach(exec_env->handle);
+    }
+    os_mutex_unlock(&cluster_list_lock);
+    return ret;
 }
 
 void
@@ -680,6 +733,14 @@ wasm_cluster_exit_thread(WASMExecEnv *exec_env, void *retval)
 int32
 wasm_cluster_cancel_thread(WASMExecEnv *exec_env)
 {
+    os_mutex_lock(&cluster_list_lock);
+    if (!clusters_have_exec_env(exec_env)) {
+        /* Invalid thread or the thread has exited */
+        os_mutex_unlock(&cluster_list_lock);
+        return 0;
+    }
+    os_mutex_unlock(&cluster_list_lock);
+
     /* Set the termination flag */
 #if WASM_ENABLE_DEBUG_INTERP != 0
     wasm_cluster_thread_send_signal(exec_env, WAMR_SIG_TERM);
diff --git a/core/iwasm/libraries/thread-mgr/thread_manager.h b/core/iwasm/libraries/thread-mgr/thread_manager.h
index e99efc99..2d4962a2 100644
--- a/core/iwasm/libraries/thread-mgr/thread_manager.h
+++ b/core/iwasm/libraries/thread-mgr/thread_manager.h
@@ -19,6 +19,7 @@ extern "C" {
 #if WASM_ENABLE_DEBUG_INTERP != 0
 typedef struct WASMDebugInstance WASMDebugInstance;
 #endif
+
 typedef struct WASMCluster {
     struct WASMCluster *next;