实验环境介绍
gcc：4.8.5glibc：glibc-2.17-222.el7.x86_64os：Centos7.4kernel：3.10.0-693.21.1.el7.x86_64
线程概念
忽略（ps：Linux是用进程实现的线程）进程是资源分配的基本单位，线程是调度的基本单位。
线程标识
忽略
线程创建
线程创建时不会保证哪个线程先执行新创建的线程会继承调用线程的浮点环境和信号屏蔽字，但是该新线程的挂起信号集会被清楚，测试代码如下：
#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <stdarg.h>
#include <signal.h>
#include <pthread.h>
#include <errno.h>
#include <unistd.h>
void sig_int(int signo
);
void *func(void *arg
);
void pr_mask(const char *str
);
int
main(int argc
, char *argv
[])
{
if (signal(SIGINT
, sig_int
) == SIG_ERR
) {
printf("register signal INT error");
exit(EXIT_FAILURE
);
}
sigset_t bset
;
sigemptyset(&bset
);
sigaddset(&bset
, SIGINT
);
if (sigprocmask(SIG_BLOCK
, &bset
, NULL) != 0) {
printf("sigprocmask() failed !\n");
return -1;
}
printf("%d: now sleep for 10 sec for waitint SIGINT\n", pthread_self());
sleep(30);
pthread_t thr1
;
if(pthread_create(&thr1
,NULL,func
, NULL)!=0) {
printf("create thread failed!\n");
return -1;
}
printf("%d: now wake and create thread over. unblock SIGINT signal\n", pthread_self());
sigset_t set
;
if (sigaddset(&set
, SIGINT
) != 0) {
printf("thread add set error\n");
}
if (sigprocmask(SIG_UNBLOCK
, &set
, NULL) != 0) {
printf("thread sigprocmask() failed !\n");
return -1;
}
printf("%d: after unblocking SIGINT, main thread sleep\n", pthread_self());
while (1) sleep(1);
return 0;
}
void
sig_int(int signo
)
{
printf("%d: SIGINT received\n", pthread_self());
}
void *func(void *arg
)
{
pr_mask("before unblock:");
while (1) sleep(1);
sigset_t set
;
if (sigaddset(&set
, SIGINT
) != 0) {
printf("thread add set error\n");
}
if (sigprocmask(SIG_UNBLOCK
, &set
, NULL) != 0) {
printf("thread sigprocmask() failed !\n");
return (void *)-1;
}
printf("%d: child thread over\n", pthread_self());
while (1) sleep(1);
return NULL;
}
void pr_mask( const char *str
){
sigset_t set
;
int errno_save
;
errno_save
= errno
;
if( sigprocmask( 0, NULL , &set
) == -1 )
printf("%d: sigprocmask error\n", pthread_self());
else {
printf( "\n%s" , str
);
if(sigismember(&set
, SIGQUIT
))
printf( " SIGQUIT" );
if(sigismember(&set
, SIGINT
))
printf( " SIGINT" );
if(sigismember(&set
, SIGUSR1
))
printf( " SIGUSR1" );
if( sigismember( &set
, SIGALRM
) )
printf( " SIGALRM" );
}
printf("\n");
errno
= errno_save
;
}
result
:
-1168320768: now sleep
for 10 sec
for waitint SIGINT
-1168320768: now wake and create thread over
. unblock SIGINT signal
before unblock
: SIGINT
-1168320768: SIGINT received
-1168320768: after unblocking SIGINT
, main thread sleep
控制终端的信号发送给该进程的主线程，测试代码如下：
#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <stdarg.h>
#include <signal.h>
#include <pthread.h>
#include <errno.h>
#include <unistd.h>
void *func(void *arg
);
void sig_int(int signo
);
int
main(int argc
, char *argv
[])
{
signal(SIGINT
, sig_int
);
pthread_t thr1
;
printf("%lu: main thread\n", pthread_self());
if(pthread_create(&thr1
,NULL,func
, NULL)!=0) {
printf("create thread failed!\n");
return -1;
}
while (1) sleep(1);
return 0;
}
void
sig_int(int signo
)
{
printf("%lu: SIGINT received\n", pthread_self());
}
void *func(void *arg
)
{
while (1) sleep(1);
return NULL;
}
result：
140463559870208: main thread
^C140463559870208
: SIGINT received
^C140463559870208
: SIGINT received
^C140463559870208
: SIGINT received
^\Quit
线程终止
线程终止的方式：
如果任意线程调用exit、_Exit或者_exit，那么整个进程就会终止如果默认的动作是终止进程，那么，发送到该线程的信号会终止整个进程（12章再来讨论信号和线程）单个线程有三种退出方式
线程可以从启动例程中返回，返回值是线程的退出码线程可以被同一进程中的其他线程取消线程调用pthread_exit来结束 相关函数：pthread_exit、pthread_join
pthread_join可以获取到pthread_exit的rval_ptr，如果线程是被取消的，则pthread_join的rval_ptr指向的内存单元为PTHREAD_CANCELEDpthread_join也自动把线程置于分离状态pthread_join可以回收同一个进程的其他线程
注意在线程函数中返回的指针是合法的，该指针的数据分配不该是在线程函数的栈上分配。这样在别的线程中进行进行join的时候，该地址已经不合法
pthread_cancel函数
该函数并不等待线程终止，它仅仅提出请求pthread_cleanup_push函数可以注册线程退出清理函数，这些清理函数被pthread_cleanup_push函数调度，pthread_cleanup_pop函数是删除线程的清理函数pthread_cleanup_push函数注册的函数的调用时机为：
pthread_exit时被别的线程进行pthread_cancel时pthread_cleanup_pop的参数非0时 测试代码如下
#include <stdio.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <stdarg.h>
#include <signal.h>
#include <pthread.h>
#include <errno.h>
#include <unistd.h>
#define MAXLINE 2048
static void
err_doit(int errnoflag
, int error
, const char *fmt
, va_list ap
)
{
char buf
[MAXLINE
];
vsnprintf(buf
, MAXLINE
-1, fmt
, ap
);
if (errnoflag
)
snprintf(buf
+strlen(buf
), MAXLINE
-strlen(buf
)-1, ": %s",
strerror(error
));
strcat(buf
, "\n");
fflush(stdout);
fputs(buf
, stderr);
fflush(NULL);
}
void
err_exit(int error
, const char *fmt
, ...)
{
va_list ap
;
va_start(ap
, fmt
);
err_doit(1, error
, fmt
, ap
);
va_end(ap
);
exit(1);
}
void
cleanup(void *arg
)
{
printf("cleanup: %s\n", (char *)arg
);
}
void *
thr_fn1(void *arg
)
{
printf("thread 1 start\n");
pthread_cleanup_push(cleanup
, "thread 1 first handler");
pthread_cleanup_push(cleanup
, "thread 1 second handler");
printf("thread 1 push complete\n");
if (arg
)
return((void *)1);
pthread_cleanup_pop(0);
pthread_cleanup_pop(0);
return((void *)1);
}
void *
thr_fn2(void *arg
)
{
printf("thread 2 start\n");
pthread_cleanup_push(cleanup
, "thread 2 first handler");
pthread_cleanup_push(cleanup
, "thread 2 second handler");
printf("thread 2 push complete\n");
if (arg
)
pthread_exit((void *)2);
pthread_cleanup_pop(0);
pthread_cleanup_pop(0);
pthread_exit((void *)2);
}
int
main(void)
{
int err
;
pthread_t tid1
, tid2
;
void *tret
;
err
= pthread_create(&tid1
, NULL, thr_fn1
, (void *)1);
if (err
!= 0)
err_exit(err
, "can't create thread 1");
err
= pthread_create(&tid2
, NULL, thr_fn2
, (void *)1);
if (err
!= 0)
err_exit(err
, "can't create thread 2");
err
= pthread_join(tid1
, &tret
);
if (err
!= 0)
err_exit(err
, "can't join with thread 1");
printf("thread 1 exit code %ld\n", (long)tret
);
err
= pthread_join(tid2
, &tret
);
if (err
!= 0)
err_exit(err
, "can't join with thread 2");
printf("thread 2 exit code %ld\n", (long)tret
);
exit(0);
}
result
:
thread
1 start
thread
1 push complete
thread
2 start
thread
2 push complete
thread
1 exit code
1
cleanup
: thread
2 second handler
cleanup
: thread
2 first handler
thread
2 exit code
2
进程和线程的原语比较：
