localtime_r在多线程环境下可能存在死锁

localtime_r是localtime的线程安全版本,在localtime的手册中描述如下:
Attention: Do not use the ctime, localtime, gmtime, or asctime subroutine in a multithreaded
environment. See the multithread alternatives in the ctime_r (ctime_r, localtime_r, gmtime_r, or
asctime_r Subroutine), localtime_r, gmtime_r, or asctime_r subroutine article.

但是在某些情况下,localtime_r可能存在死锁的情况,使用如下的测试程序:

#include <pthread.h>
#include <time.h>

void *mytest(void *arg)
{
pthread_detach(pthread_self());

time_t current;
struct tm date;
time(¤t);

while (1) {
localtime_r(¤t, &date);
printf("OK/n");
}
}

int main()
{
int i = 0;
pthread_t tid[10];

for (i = 0; i < 10; i++) {
pthread_create(&tid[i], NULL, mytest, NULL);
}

sleep(1);

pthread_cancel(tid[0]);
pthread_cancel(tid[1]);
pthread_cancel(tid[2]);
pthread_cancel(tid[3]);

while (1)
sleep(100000000);
}

运行该测试程序, 大约1秒之后, 屏幕不再输出任何信息,使用dbx跟踪程序如下:
(dbx) thread
thread state-k wchan state-u k-tid mode held scope function
$t1 wait 0xf100060027c244b0 running 7172309 k no sys nsleep
*$t2 run blocked 7176385 k no sys _global_lock_common
$t3 wait 0x000000011000ad18 blocked 3379347 k no sys _rec_mutex_lock
$t4 zomb terminated 7180483 k no sys pthread_exit
$t5 wait 0x000000011000ad18 blocked 9109677 k no sys _rec_mutex_lock
>$t6 wait 0x000000011000ad18 blocked 3498171 k no sys _rec_mutex_lock
$t7 wait 0x000000011000ad18 blocked 3502269 k no sys _rec_mutex_lock
$t8 wait 0x000000011000ad18 blocked 3506367 k no sys _rec_mutex_lock
$t9 wait 0x000000011000ad18 blocked 2384027 k no sys _rec_mutex_lock
$t10 wait 0x000000011000ad18 blocked 2932903 k no sys _rec_mutex_lock
$t11 wait 0x000000011000ad18 blocked 2494699 k no sys _rec_mutex_lock
(dbx) where
_rec_mutex_lock(??) at 0x900000000028f90
localtime_tz_r(??, ??, ??) at 0x900000000055644
mytest(0x0) at 0x1000005fc

所有的线程都在试图获取锁，进程处于死锁状态。目前AIX工程师给出的临时解决方案是将环境变量TZ设置为BEIST，
export TZ=BEIST
之后再运行测试程序就没有死锁的现象。由于TZ是一个系统环境变量，修改之后可能会引起其他系统出问题.