我如何检查当前线程是否是
linux上的主线程？看起来gettid()只返回一个pid,但似乎linux不保证main()的线程总是有一个const和统一的pid.
原因是我有一个自动并行化,我想确保pthread_create()没有被一个已经在由pthread_create()创建的线程上运行的函数中调用.
对于
Linux：
如果getpid()返回与gettid()相同的结果,那么它是主线程.
int i_am_the_main_thread(void)
{
return getpid() == gettid();
}
从man gettid：
gettid() returns the caller’s thread ID (TID). In a single-threaded process,the thread ID is equal to the process ID (PID,as returned by getpid(2)). In a multithreaded process,all threads have the same PID,but each one
has a unique TID.
从man clone：
Thread groups were a feature added in Linux 2.4 to support the
POSIX threads notion of a set of threads that share a single
PID. Internally,this shared PID is the so-called thread
group identifier (TGID) for the thread group. Since Linux
2.4,calls to getpid(2) return the TGID of the caller.
The threads within a group can be distinguished by their
(system-wide) unique thread IDs (TID). A new thread’s TID is
available as the function result returned to the caller of
clone(),and a thread can obtain its own TID using gettid(2).
