Implement async termination of blocking thread (#2516)

Send a signal whose handler is no-op to a blocking thread to wake up
the blocking syscall with either EINTR equivalent or partial success.

Unlike the approach taken in the `dev/interrupt_block_insn` branch (that is,
signal + longjmp similarly to `OS_ENABLE_HW_BOUND_CHECK`), this PR
does not use longjmp because:
* longjmp from signal handler doesn't work on nuttx
  refer to https://github.com/apache/nuttx/issues/10326
* the singal+longjmp approach may be too difficult for average programmers
  who might implement host functions to deal with

See also https://github.com/bytecodealliance/wasm-micro-runtime/issues/1910

core/shared/platform/common/posix/posix_blocking_op.c

@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2023 Midokura Japan KK.  All rights reserved.
+ * SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+ */
+
+#include "platform_api_extension.h"
+
+#ifdef OS_ENABLE_WAKEUP_BLOCKING_OP
+
+static bool g_blocking_op_inited = false;
+static int g_blocking_op_signo = SIGUSR1;
+static sigset_t g_blocking_op_sigmask;
+
+static void
+blocking_op_sighandler(int signo)
+{
+    /* nothing */
+}
+
+void
+os_set_signal_number_for_blocking_op(int signo)
+{
+    g_blocking_op_signo = signo;
+}
+
+int
+os_blocking_op_init()
+{
+    if (g_blocking_op_inited) {
+        return BHT_OK;
+    }
+
+    sigemptyset(&g_blocking_op_sigmask);
+    sigaddset(&g_blocking_op_sigmask, g_blocking_op_signo);
+
+    struct sigaction sa;
+    sigemptyset(&sa.sa_mask);
+    sa.sa_flags = 0;
+    sa.sa_handler = blocking_op_sighandler;
+    if (sigaction(g_blocking_op_signo, &sa, NULL)) {
+        return BHT_ERROR;
+    }
+    g_blocking_op_inited = true;
+    return BHT_OK;
+}
+
+void
+os_begin_blocking_op()
+{
+    pthread_sigmask(SIG_UNBLOCK, &g_blocking_op_sigmask, NULL);
+}
+
+void
+os_end_blocking_op()
+{
+    pthread_sigmask(SIG_BLOCK, &g_blocking_op_sigmask, NULL);
+}
+
+int
+os_wakeup_blocking_op(korp_tid tid)
+{
+    int ret = pthread_kill(tid, g_blocking_op_signo);
+    if (ret != 0) {
+        return BHT_ERROR;
+    }
+    return BHT_OK;
+}
+
+#endif /* OS_ENABLE_WAKEUP_BLOCKING_OP */

core/shared/platform/common/posix/posix_thread.c

@@ -39,6 +39,9 @@ os_thread_wrapper(void *arg)
 #ifdef OS_ENABLE_HW_BOUND_CHECK
     if (os_thread_signal_init(handler) != 0)
         return NULL;
+#endif
+#ifdef OS_ENABLE_WAKEUP_BLOCKING_OP
+    os_end_blocking_op();
 #endif
     start_func(thread_arg);
 #ifdef OS_ENABLE_HW_BOUND_CHECK

core/shared/platform/darwin/platform_internal.h

@@ -102,6 +102,12 @@ os_sigreturn();
 #endif /* end of BUILD_TARGET_X86_64/AMD_64/AARCH64/RISCV64 */
 #endif /* end of WASM_DISABLE_HW_BOUND_CHECK */
 
+#if WASM_DISABLE_WAKEUP_BLOCKING_OP != 0
+#define OS_ENABLE_WAKEUP_BLOCKING_OP
+#endif
+void
+os_set_signal_number_for_blocking_op(int signo);
+
 #ifdef __cplusplus
 }
 #endif

core/shared/platform/freebsd/platform_internal.h

@@ -101,6 +101,12 @@ os_sigreturn();
 #endif /* end of BUILD_TARGET_X86_64/AMD_64/AARCH64/RISCV64 */
 #endif /* end of WASM_DISABLE_HW_BOUND_CHECK */
 
+#if WASM_DISABLE_WAKEUP_BLOCKING_OP != 0
+#define OS_ENABLE_WAKEUP_BLOCKING_OP
+#endif
+void
+os_set_signal_number_for_blocking_op(int signo);
+
 #ifdef __cplusplus
 }
 #endif

core/shared/platform/include/platform_api_extension.h

@@ -323,6 +323,34 @@ os_sem_getvalue(korp_sem *sem, int *sval);
 int
 os_sem_unlink(const char *name);
 
+/**
+ * Initialize process-global state for os_wakeup_blocking_op.
+ */
+int
+os_blocking_op_init();
+
+/**
+ * Start accepting os_wakeup_blocking_op requests for the calling thread.
+ */
+void
+os_begin_blocking_op();
+
+/**
+ * Stop accepting os_wakeup_blocking_op requests for the calling thread.
+ */
+void
+os_end_blocking_op();
+
+/**
+ * Wake up the specified thread.
+ *
+ * For example, on posix-like platforms, this can be implemented by
+ * sending a signal (w/o SA_RESTART) which interrupts a blocking
+ * system call.
+ */
+int
+os_wakeup_blocking_op(korp_tid tid);
+
 /****************************************************
  *                     Section 2                    *
  *                   Socket support                 *

core/shared/platform/linux/platform_internal.h

@@ -115,6 +115,12 @@ os_sigreturn();
 #endif /* end of BUILD_TARGET_X86_64/AMD_64/AARCH64/RISCV64 */
 #endif /* end of WASM_DISABLE_HW_BOUND_CHECK */
 
+#if WASM_DISABLE_WAKEUP_BLOCKING_OP != 0
+#define OS_ENABLE_WAKEUP_BLOCKING_OP
+#endif
+void
+os_set_signal_number_for_blocking_op(int signo);
+
 #ifdef __cplusplus
 }
 #endif

core/shared/platform/nuttx/platform_internal.h

@@ -123,6 +123,12 @@ utimensat(int fd, const char *path, const struct timespec ts[2], int flag);
 DIR *
 fdopendir(int fd);
 
+#if WASM_DISABLE_WAKEUP_BLOCKING_OP != 0
+#define OS_ENABLE_WAKEUP_BLOCKING_OP
+#endif
+void
+os_set_signal_number_for_blocking_op(int signo);
+
 #ifdef __cplusplus
 }
 #endif