why pthread causes a memory leak
每当我创建pthread时,valgrind都会输出内存泄漏,
例如下面的代码:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 | #include <stdio.h> #include <unistd.h> #include <pthread.h> void *timer1_function (void *eit){ (void) eit; printf("hello world\ "); pthread_exit(NULL); } int main(void){ pthread_t timer1; pthread_create( &timer1, NULL, timer1_function, NULL); ///////line13 int i=0; for(i=0;i<2;i++){usleep(1);} return 0; } |
valgrind输出
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 | ==1395== HEAP SUMMARY: ==1395== in use at exit: 136 bytes in 1 blocks ==1395== total heap usage: 6 allocs, 5 frees, 1,134 bytes allocated ==1395== ==1395== 136 bytes in 1 blocks are possibly lost in loss record 1 of 1 ==1395== at 0x402A629: calloc (in /usr/lib/valgrind/vgpreload_memcheck-x86-linux.so) ==1395== by 0x4011304: allocate_dtv (dl-tls.c:297) ==1395== by 0x4011AAB: _dl_allocate_tls (dl-tls.c:461) ==1395== by 0x4052470: pthread_create@@GLIBC_2.1 (allocatestack.c:571) ==1395== by 0x8048566: main (test.c:13) ==1395== ==1395== LEAK SUMMARY: ==1395== definitely lost: 0 bytes in 0 blocks ==1395== indirectly lost: 0 bytes in 0 blocks ==1395== possibly lost: 136 bytes in 1 blocks ==1395== still reachable: 0 bytes in 0 blocks ==1395== suppressed: 0 bytes in 0 blocks |
尽管我使用手册页作为参考,为什么pthread_create会引起问题,我该如何解决?
线程是分配的资源,您没有在退出之前释放它。您应该致电
即使您修复了此问题,由于POSIX线程的某些实现(我猜您正在使用glibc / NPTL)缓存并重用线程资源而不是完全释放线程资源,所以valgrind仍然可能会出现"泄漏"。我不确定valgrind是否可以解决此问题。
我认为
"
1 | pthread_join(timer1, NULL); |
显示的泄漏与在子线程的本地存储(tls)中分配的DTV(动态线程矢量)结构有关。
在主线程(即产生子代的线程)中使用
对于不需要
来自
The
pthread_detach() function marks the thread identified by thread
as detached. When a detached thread terminates, its resources are
automatically released back to the system without the need for
another thread to join with the terminated thread.
当我无法调用pthread_join时,我看到了类似的结果。
当我调用pthread_join时,Valgrind将指示没有内存错误或泄漏。使用pthread_kill查看线程是否仍然存在,然后调用join清理和释放资源,得到了一个干净的结果。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | int stop_worker(worker_t *self) { if (self) { // signal the thread to quit // (here using a variable and semaphore) self->thread_quit=TRUE; sem_post(&self->sem); // wait for it to stop // (could use counter, etc. to limit wait) int test=0; while (pthread_kill(self->thread,0) == 0) { MDEBUG(MD_XF_LOGGER,"waiting for thread to exit...\ ",test); delay_msec(50); } // even though thread is finished, need to call join // otherwise, it will not release its memory (and valgrind indicates a leak) test=pthread_join(self->thread,NULL); return 0; } return -1; } |
内存泄漏是由于以下事实导致的:如果线程不取消就保持运行状态,则不会释放相应的动态分配的内存。将pthread_cancel()连同pthread_cleanup_push(CleanupHandler,NULL)和pthread_cleanup_pop(0)一起使用,可以在取消后进行线程清理。