pthread_create()-------Resource temporarily unavailable

喜欢ヅ旅行 2022-08-06 14:16 17阅读 0赞

最近在IOS设备上使用底层C++开发一个HTTP模块，使用了多线程pthread\_create()，为了想测试模块的稳定性，创建了大量的线程进行测试。当线程达到一定数量时发现再调用pthread\_create()开始返回错误值Resource temporarily unavailable。

代码如下：

int err = pthread\_create(&threadID, &attr, ThreadEntery, this);

if (err!=0) \{

cout<<"can't create thread: %s"<<strerror(err)<<endl;

pthread\_attr\_destroy(&attr);

原因就是线程结束时没有释放资源。具体参看下面的资料。

原文地址：[http://www.cppblog.com/prayer/archive/2012/04/23/172427.html][http_www.cppblog.com_prayer_archive_2012_04_23_172427.html]

这两天在看Pthread 资料的时候，无意中看到[这样][Link 1]一句话(man pthread\_detach):

Either pthread_join(3) or pthread_detach() should be called for each thread
           that an application creates, so that system resources for the thread can be
           released.  (But note that the resources of all threads are freed when the
           process terminates.)

也就是说：每个进程创建以后都应该调用pthread\_join 或 pthread\_detach 函数，只有这样在线程结束的时候资源(线程的描述信息和stack)才能被释放.

之后又查了pthread\_join 但是没有明确说明必须调用pthread\_join 或 pthread\_detach.

但是再查了 Pthread for win32 [pthread\_join][pthread_join]

When a joinable thread terminates, its memory resources (thread descriptor and stack) are not deallocated until another thread performs pthread\_join on it. Therefore, pthread\_join must be called once for each joinable thread created to avoid **memory leaks**.

才知道如果在新线程里面没有调用pthread\_join 或 pthread\_detach会导致内存泄漏, 如果你创建的线程越多，你的内存利用率就会越高, 直到你再无法创建线程，最终只能结束进程。

解决方法有三个:

1. 线程里面调用 ***pthread\_detach(pthread\_self())* 这个方法最简单**

2 **. 在创建线程的设置*PTHREAD\_CREATE\_DETACHED*属性**

**3. 创建线程后用 *pthread\_join()* 一直等待子线程结束。**

下面是几个简单的例子

1. 调用 ***pthread\_detach(pthread\_self())***

\#include <stdio.h>

\#include <stdlib.h>

\#include <pthread.h>

void \*PrintHello(void)

pthread\_detach(pthread\_self());

int stack\[1024 \* 20\] = \{0,\};

//sleep(1);

long tid = 0;

//printf(“Hello World! It’s me, thread \#%ld!\\n”, tid);

//pthread\_exit(NULL);

int main (int argc, char \*argv\[\])

pthread\_t pid;

int rc;

long t;

while (1) \{

printf(“In main: creating thread %ld\\n”, t);

rc = pthread\_create(&pid, NULL, PrintHello, NULL);

if (rc)\{

printf(“ERROR; return code from pthread\_create() is %d\\n”, rc);

//exit(-1);

sleep(1);

printf(” \\n— main End —- \\n”);

pthread\_exit(NULL);

2 **. 在创建线程的设置PTHREAD\_CREATE\_DETACHED属性**

\#include <stdio.h>

\#include <stdlib.h>

\#include <pthread.h>

void \*PrintHello(void)

int stack\[1024 \* 20\] = \{0,\};

//pthread\_exit(NULL);

//pthread\_detach(pthread\_self());

int main (int argc, char \*argv\[\])

pthread\_t pid;

int rc;

long t;

while (1) \{

printf(“In main: creating thread %ld\\n”, t);

pthread\_attr\_t attr;

pthread\_t thread;

pthread\_attr\_init (&attr);

pthread\_attr\_setdetachstate (&attr, PTHREAD\_CREATE\_DETACHED);

rc = pthread\_create(&pid, &attr, PrintHello, NULL);

pthread\_attr\_destroy (&attr);

if (rc)\{

printf(“ERROR; return code from pthread\_create() is %d\\n”, rc);

//exit(-1);

sleep(1);

printf(” \\n— main End —- \\n”);

pthread\_exit(NULL);

3. 创建线程后用 pthread\_join() 一直等待子线程结束。

\#include <stdio.h>

\#include <stdlib.h>

\#include <pthread.h>

void \*PrintHello(void)

int stack\[1024 \* 20\] = \{0,\};

//sleep(1);

long tid = 0;

//pthread\_exit(NULL);

//pthread\_detach(pthread\_self());

int main (int argc, char \*argv\[\])

pthread\_t pid;

int rc;

long t;

while (1) \{

printf(“In main: creating thread %ld\\n”, t);

rc = pthread\_create(&pid, NULL, PrintHello, NULL);

if (rc)\{

printf(“ERROR; return code from pthread\_create() is %d\\n”, rc);

//exit(-1);

pthread\_join(pid, NULL);

sleep(1);

printf(” \\n— main End —- \\n”);

pthread\_exit(NULL);

[http_www.cppblog.com_prayer_archive_2012_04_23_172427.html]: http://www.cppblog.com/prayer/archive/2012/04/23/172427.html
[Link 1]: http://www.kernel.org/doc/man-pages/online/pages/man3/pthread_detach.3.html
[pthread_join]: http://sourceware.org/pthreads-win32/manual/pthread_join.html