问题的由来是这样的，有个开源项目jcgroup（Cgroup on JVM），其中有一些功能需要获取当前线程的id。jcgroup通过native的方式获取，但是在Mac下行不通。
Windows，Linux下可以通过JNA jar获取gettid
import com.sun.jna.Library;
import com.sun.jna.Native;
import com.sun.jna.Platform;
public class Threads {
private interface CLibrary extends Library {
CLibrary INSTANCE = (CLibrary) Native.loadLibrary(Platform.isWindows() ? "msvcrt" : "c", CLibrary.class);
int syscall(int api);
}
private static final int __NR_gettid = Platform.isMac() ? 286 : (Platform.is64Bit() ? 186 : 224);
public static int getThreadId() {
return CLibrary.INSTANCE.syscall(__NR_gettid);
}
}
Mac系统执行结果是 -1
Mac系统有什么办法可以获取线程id呢？
这时想到了Golang，查看api
func Gettid() (tid int)
但是不幸的是，Golang在Mac下没有提供这个函数（作罢）
Google下：
MacOS: use SYSthreadselfid for thread id
SYSgettid is instead some kind of effective uid. SYSthread_selfid was added in 10.6, so we simply do not support 10.5 or earlier.
Index: core/unix/os.c
diff --git a/core/unix/os.c b/core/unix/os.c
index 4d94fff09ea5dcbfc038baf44ef8f4dd63043623..48d6e7208f755bcf96106cec2406f3e43728b67e 100644
--- a/core/unix/os.c
+++ b/core/unix/os.c
@@ -1,5 +1,5 @@
/* *******************************************************************************
- * Copyright (c) 2010-2013 Google, Inc. All rights reserved.
+ * Copyright (c) 2010-2014 Google, Inc. All rights reserved.
* Copyright (c) 2011 Massachusetts Institute of Technology All rights reserved.
* Copyright (c) 2000-2010 VMware, Inc. All rights reserved.
* *******************************************************************************/
@@ -687,10 +687,24 @@ os_init(void)
* or whether getpid suffices. even 2.4 kernels have gettid
* (maps to getpid), don't have an old enough target to test this.
*/
+#ifdef MACOS
+ kernel_thread_groups = (dynamorio_syscall(SYS_thread_selfid, 0) >= 0);
+#else
kernel_thread_groups = (dynamorio_syscall(SYS_gettid, 0) >= 0);
+#endif
LOG(GLOBAL, LOG_TOP|LOG_STATS, 1, "thread id is from %s\n",
kernel_thread_groups ? "gettid" : "getpid");
+#ifdef MACOS
+ /* SYS_thread_selfid was added in 10.6. We have no simple way to get the
+ * thread id on 10.5, so we don't support it.
+ */
+ if (!kernel_thread_groups) {
+ SYSLOG(SYSLOG_WARNING, UNSUPPORTED_OS_VERSION, 3,
+ get_application_name(), get_application_pid(), "Mac OSX 10.5 or earlier");
+ }
+#else
ASSERT_CURIOSITY(kernel_thread_groups);
+#endif
pid_cached = get_process_id();
@@ -1898,11 +1912,14 @@ get_parent_id(void)
thread_id_t
get_sys_thread_id(void)
{
- if (kernel_thread_groups) {
+#ifdef MACOS
+ if (kernel_thread_groups)
+ return dynamorio_syscall(SYS_thread_selfid, 0);
+#else
+ if (kernel_thread_groups)
return dynamorio_syscall(SYS_gettid, 0);
- } else {
- return dynamorio_syscall(SYS_getpid, 0);
- }
+#endif
+ return dynamorio_syscall(SYS_getpid, 0);
}
thread_id_t
#include <iostream>
#include <pthread.h>
#include <sys/syscall.h>
int main(int argc, const char * argv[]) {
std::cout << "getpid()=" << getpid() << std::endl;
std::cout << "pthread_self()=" << pthread_self() << std::endl;
uint64_t tid;
pthread_threadid_np(NULL, &tid);
std::cout << "pthread_threadid_np()=" << tid << std::endl;
std::cout << "syscall(SYS_thread_selfid)=" << syscall(SYS_thread_selfid) << std::endl;
std::cout << "syscall(SYS_gettid)=" << syscall(SYS_gettid) << std::endl;
return 0;
}
/*
* getpid()=1753
* pthread_self()=0x100081000
* pthread_threadid_np()=84638
* syscall(SYS_thread_selfid)=84638
* syscall(SYS_gettid)=-1
*/
验证，SYSthreadselfid并非线程id