thread-mgr: Fix spread "wasi proc exit" exception and atomic.wait issues (bytecodealliance#1988)

Raising "wasi proc exit" exception, spreading it to other threads and then
clearing it in all threads may result in unexpected behavior: the sub thread
may end first, handle the "wasi proc exit" exception and clear exceptions
of other threads, including the main thread. And when main thread's
exception is cleared, it may continue to run and throw "unreachable"
exception. This also leads to some assertion failed.

Ignore exception spreading for "wasi proc exit" and don't clear exception
of other threads to resolve the issue.

And add suspend flag check after atomic wait since the atomic wait may
be notified by other thread when exception occurs.

Author: wenyongh

core/iwasm/common/wasm_runtime_common.c

@@ -1880,8 +1880,10 @@ clear_wasi_proc_exit_exception(WASMModuleInstanceCommon *module_inst_comm)
     if (exception && !strcmp(exception, "Exception: wasi proc exit")) {
         /* The "wasi proc exit" exception is thrown by native lib to
            let wasm app exit, which is a normal behavior, we clear
-           the exception here. */
-        wasm_set_exception(module_inst, NULL);
+           the exception here. And just clear the exception of current
+           thread, don't call `wasm_set_exception(module_inst, NULL)`
+           which will clear the exception of all threads. */
+        module_inst->cur_exception[0] = '\0';
         return true;
     }
     return false;

core/iwasm/compilation/aot_emit_function.c

@@ -999,6 +999,14 @@ aot_compile_op_call(AOTCompContext *comp_ctx, AOTFuncContext *func_ctx,
     }
 #endif
 
+#if WASM_ENABLE_THREAD_MGR != 0
+    /* Insert suspend check point */
+    if (comp_ctx->enable_thread_mgr) {
+        if (!check_suspend_flags(comp_ctx, func_ctx))
+            goto fail;
+    }
+#endif
+
     ret = true;
 fail:
     if (param_types)
@@ -1645,6 +1653,14 @@ aot_compile_op_call_indirect(AOTCompContext *comp_ctx, AOTFuncContext *func_ctx,
     }
 #endif
 
+#if WASM_ENABLE_THREAD_MGR != 0
+    /* Insert suspend check point */
+    if (comp_ctx->enable_thread_mgr) {
+        if (!check_suspend_flags(comp_ctx, func_ctx))
+            goto fail;
+    }
+#endif
+
     ret = true;
 
 fail:

core/iwasm/compilation/aot_emit_memory.c

@@ -7,6 +7,7 @@
 #include "aot_emit_exception.h"
 #include "../aot/aot_runtime.h"
 #include "aot_intrinsic.h"
+#include "aot_emit_control.h"
 
 #define BUILD_ICMP(op, left, right, res, name)                                \
     do {                                                                      \
@@ -1344,7 +1345,7 @@ aot_compile_op_atomic_wait(AOTCompContext *comp_ctx, AOTFuncContext *func_ctx,
         return false;
     }
 
-    BUILD_ICMP(LLVMIntSGT, ret_value, I32_ZERO, cmp, "atomic_wait_ret");
+    BUILD_ICMP(LLVMIntNE, ret_value, I32_NEG_ONE, cmp, "atomic_wait_ret");
 
     ADD_BASIC_BLOCK(wait_fail, "atomic_wait_fail");
     ADD_BASIC_BLOCK(wait_success, "wait_success");
@@ -1368,6 +1369,14 @@ aot_compile_op_atomic_wait(AOTCompContext *comp_ctx, AOTFuncContext *func_ctx,
 
     PUSH_I32(ret_value);
 
+#if WASM_ENABLE_THREAD_MGR != 0
+    /* Insert suspend check point */
+    if (comp_ctx->enable_thread_mgr) {
+        if (!check_suspend_flags(comp_ctx, func_ctx))
+            return false;
+    }
+#endif
+
     return true;
 fail:
     return false;

core/iwasm/interpreter/wasm_interp_classic.c

@@ -3422,6 +3422,10 @@ wasm_interp_call_func_bytecode(WASMModuleInstance *module,
                         if (ret == (uint32)-1)
                             goto got_exception;
 
+#if WASM_ENABLE_THREAD_MGR != 0
+                        CHECK_SUSPEND_FLAGS();
+#endif
+
                         PUSH_I32(ret);
                         break;
                     }
@@ -3442,6 +3446,10 @@ wasm_interp_call_func_bytecode(WASMModuleInstance *module,
                         if (ret == (uint32)-1)
                             goto got_exception;
 
+#if WASM_ENABLE_THREAD_MGR != 0
+                        CHECK_SUSPEND_FLAGS();
+#endif
+
                         PUSH_I32(ret);
                         break;
                     }
@@ -3894,10 +3902,10 @@ wasm_interp_call_func_bytecode(WASMModuleInstance *module,
             PUSH_CSP(LABEL_TYPE_FUNCTION, 0, cell_num, frame_ip_end - 1);
 
             wasm_exec_env_set_cur_frame(exec_env, frame);
+        }
 #if WASM_ENABLE_THREAD_MGR != 0
-            CHECK_SUSPEND_FLAGS();
+        CHECK_SUSPEND_FLAGS();
 #endif
-        }
         HANDLE_OP_END();
     }
 

core/iwasm/interpreter/wasm_interp_fast.c

@@ -3266,6 +3266,10 @@ wasm_interp_call_func_bytecode(WASMModuleInstance *module,
                         if (ret == (uint32)-1)
                             goto got_exception;
 
+#if WASM_ENABLE_THREAD_MGR != 0
+                        CHECK_SUSPEND_FLAGS();
+#endif
+
                         PUSH_I32(ret);
                         break;
                     }
@@ -3286,6 +3290,10 @@ wasm_interp_call_func_bytecode(WASMModuleInstance *module,
                         if (ret == (uint32)-1)
                             goto got_exception;
 
+#if WASM_ENABLE_THREAD_MGR != 0
+                        CHECK_SUSPEND_FLAGS();
+#endif
+
                         PUSH_I32(ret);
                         break;
                     }
@@ -3826,6 +3834,9 @@ wasm_interp_call_func_bytecode(WASMModuleInstance *module,
 
             wasm_exec_env_set_cur_frame(exec_env, (WASMRuntimeFrame *)frame);
         }
+#if WASM_ENABLE_THREAD_MGR != 0
+        CHECK_SUSPEND_FLAGS();
+#endif
         HANDLE_OP_END();
     }
 

core/iwasm/libraries/thread-mgr/thread_manager.c

@@ -225,7 +225,9 @@ wasm_cluster_create(WASMExecEnv *exec_env)
     /* Prepare the aux stack top and size for every thread */
     if (!wasm_exec_env_get_aux_stack(exec_env, &aux_stack_start,
                                      &aux_stack_size)) {
+#if WASM_ENABLE_LIB_WASI_THREADS == 0
         LOG_VERBOSE("No aux stack info for this module, can't create thread");
+#endif
 
         /* If the module don't have aux stack info, don't throw error here,
             but remain stack_tops and stack_segment_occupied as NULL */
@@ -1131,9 +1133,14 @@ set_exception_visitor(void *node, void *user_data)
         WASMModuleInstance *curr_wasm_inst =
             (WASMModuleInstance *)get_module_inst(curr_exec_env);
 
-        bh_memcpy_s(curr_wasm_inst->cur_exception,
-                    sizeof(curr_wasm_inst->cur_exception),
-                    wasm_inst->cur_exception, sizeof(wasm_inst->cur_exception));
+        /* Only spread non "wasi proc exit" exception */
+        if (!strstr(wasm_inst->cur_exception, "wasi proc exit")) {
+            bh_memcpy_s(curr_wasm_inst->cur_exception,
+                        sizeof(curr_wasm_inst->cur_exception),
+                        wasm_inst->cur_exception,
+                        sizeof(wasm_inst->cur_exception));
+        }
+
         /* Terminate the thread so it can exit from dead loops */
         set_thread_cancel_flags(curr_exec_env);
     }
@@ -1203,4 +1210,4 @@ bool
 wasm_cluster_is_thread_terminated(WASMExecEnv *exec_env)
 {
     return (exec_env->suspend_flags.flags & 0x01) ? true : false;
-}
+}

samples/wasi-threads/README.md

@@ -26,6 +26,7 @@ $ ./iwasm wasm-apps/exception_propagation.wasm
 ## Run samples in AOT mode
 ```shell
 $ ../../../wamr-compiler/build/wamrc \
+    --enable-multi-thread \
     -o wasm-apps/no_pthread.aot wasm-apps/no_pthread.wasm
 $ ./iwasm wasm-apps/no_pthread.aot
 ```

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

@@ -15,8 +15,14 @@
 
 #include "wasi_thread_start.h"
 
-#define TEST_TERMINATION_BY_TRAP 0 // Otherwise test `proc_exit` termination
-#define TEST_TERMINATION_IN_MAIN_THREAD 1
+#define BUSY_WAIT 0
+#define ATOMIC_WAIT 1
+#define POLL_ONEOFF 2
+
+/* Change parameters here to modify the sample behavior */
+#define TEST_TERMINATION_BY_TRAP 0 /* Otherwise `proc_exit` termination */
+#define TEST_TERMINATION_IN_MAIN_THREAD 1 /* Otherwise in spawn thread */
+#define LONG_TASK_IMPL ATOMIC_WAIT
 
 #define TIMEOUT_SECONDS 10
 #define NUM_THREADS 3
@@ -30,23 +36,28 @@ typedef struct {
 void
 run_long_task()
 {
-    // Busy waiting to be interruptible by trap or `proc_exit`
+#if LONG_TASK_IMPL == BUSY_WAIT
     for (int i = 0; i < TIMEOUT_SECONDS; i++)
         sleep(1);
+#elif LONG_TASK_IMPL == ATOMIC_WAIT
+    __builtin_wasm_memory_atomic_wait32(0, 0, -1);
+#else
+    sleep(TIMEOUT_SECONDS);
+#endif
 }
 
 void
 start_job()
 {
     sem_post(&sem);
-    run_long_task(); // Wait to be interrupted
+    run_long_task(); /* Wait to be interrupted */
     assert(false && "Unreachable");
 }
 
 void
 terminate_process()
 {
-    // Wait for all other threads (including main thread) to be ready
+    /* Wait for all other threads (including main thread) to be ready */
     printf("Waiting before terminating\n");
     for (int i = 0; i < NUM_THREADS; i++)
         sem_wait(&sem);
@@ -55,7 +66,7 @@ terminate_process()
 #if TEST_TERMINATION_BY_TRAP == 1
     __builtin_trap();
 #else
-    __wasi_proc_exit(1);
+    __wasi_proc_exit(33);
 #endif
 }
 
@@ -86,14 +97,14 @@ main(int argc, char **argv)
     }
 
     for (i = 0; i < NUM_THREADS; i++) {
-        // No graceful memory free to simplify the example
+        /* No graceful memory free to simplify the example */
         if (!start_args_init(&data[i].base)) {
             printf("Failed to allocate thread's stack\n");
             return EXIT_FAILURE;
         }
     }
 
-// Create a thread that forces termination through trap or `proc_exit`
+    /* Create a thread that forces termination through trap or `proc_exit` */
 #if TEST_TERMINATION_IN_MAIN_THREAD == 1
     data[0].throw_exception = false;
 #else
@@ -105,7 +116,7 @@ main(int argc, char **argv)
         return EXIT_FAILURE;
     }
 
-    // Create two additional threads to test exception propagation
+    /* Create two additional threads to test exception propagation */
     data[1].throw_exception = false;
     thread_id = __wasi_thread_spawn(&data[1]);
     if (thread_id < 0) {
@@ -128,4 +139,4 @@ main(int argc, char **argv)
     start_job();
 #endif /* TEST_TERMINATION_IN_MAIN_THREAD */
     return EXIT_SUCCESS;
-}
+}