POSIX 线程 – pthread_sigmask

http://www.cnblogs.com/qq78292959/archive/2012/04/05/2432985.html

概念

按照 POSIX, 异步 (外部) 信号发送到整个进程.所有线程共享同一个设置, 即通过 sigaction 设置的线程处置方法.每个线程有自己的信号掩码, 线程库根据该掩码决定将信号发送到哪个线程.由于 Linux 线程实现上的独特性, 外部信号始终发送到特定的线程.

pthread_sigmask

pthread_sigmask 用来定义线程的信号掩码其接口与 sigprocmask 一样

===============================================================================
#include <pthread.h>
#include <signal.h>

int pthread_sigmask (int how, const sigset_t *newmask, sigset_t *oldmask);
===============================================================================

pthread_kill 和 sigwait

===============================================================================
#include <pthread.h>
#include <signal.h>

int pthread_kill (pthread_t thread, int signo);
int sigwait (const sigset_t *set, int *sig);
===============================================================================
#define ESRCH 3 /* No such process */

pthread_kill 向特定的线程发送信号.请在创建的线程中使用signal(SIGKILL,sig_handler)处理信号，如果你给一个线程发送了SIGQUIT，但线程却没有实现signal处理函数，则整个进程退出。
if(pthread_kill(pid, 0)!= ESRCH){printf("thread %d exists!\n", pid);pthread_kill(pid, SIGQUIT);// pthread_exit(NULL);//this won't workprintf("after kill\n");}sigwait 暂定调用线程, 直到 set 中定义的某个信号递达调用线程.sigwait 返回时, sig 中保存的是接收到的信号编号.sigwait 所等待的信号必须在所有线程中阻塞, 而不仅仅是调用线程. 在多线程的程序里，希望只在主线程中处理信号，可以使用函数：int pthread_sigmask (int how,const sigset_t *set,sigset_t *oset)用作在主调线程里控制信号掩码。注：新的信号屏蔽字由参数set指定，而原先的信号屏蔽字将保存到信号集oset中How:SIG_BLOCK: 结果集是当前集合参数集的并集（把参数set中的信号添加到信号屏蔽字中）
SIG_UNBLOCK: 结果集是当前集合参数集的差集（把信号屏蔽字设置为参数set中的信号）
SIG_SETMASK: 结果集是由参数集指向的集（从信号屏蔽字中删除参数set中的信号）头文件： <signal.h>错误： [EINVAL] how不是已定义值
提示： 除非信号在所有的线程里都阻塞，否则总能将异步信号传输给这个进程。例子：#include <pthread.h>#include <stdio.h>#include <sys/signal.h>#define NUMTHREADS 3void sighand(int signo);void *threadfunc(void *parm){pthread_t tid = pthread_self();int rc;printf("Thread %u entered\n", tid);rc = sleep(30);printf("Thread %u did not get expected results! rc=%d\n", tid, rc);return NULL;}void *threadmasked(void *parm){pthread_t tid = pthread_self();sigset_t mask;int rc;printf("Masked thread %lu entered\n", tid);sigfillset(&mask); /* Mask all allowed signals */rc = pthread_sigmask(SIG_BLOCK, &mask, NULL);if (rc != 0){printf("%d, %s\n", rc, strerror(rc));return NULL;}rc = sleep(15);if (rc != 0){printf("Masked thread %lu did not get expected results! ""rc=%d \n", tid, rc);return NULL;}printf("Masked thread %lu completed masked work\n",tid);return NULL;}int main(int argc, char **argv){int rc;int i;struct sigaction actions;pthread_t threads[NUMTHREADS];pthread_t maskedthreads[NUMTHREADS];printf("Enter Testcase - %s\n", argv[0]);printf("Set up the alarm handler for the process\n");memset(&actions, 0, sizeof(actions));sigemptyset(&actions.sa_mask);actions.sa_flags = 0;actions.sa_handler = sighand;rc = sigaction(SIGALRM,&actions,NULL);printf("Create masked and unmasked threads\n");for(i=0; i<NUMTHREADS; ++i){rc = pthread_create(&threads[i], NULL, threadfunc, NULL);if (rc != 0){printf("%d, %s\n", rc, strerror(rc));return -1;}rc = pthread_create(&maskedthreads[i], NULL, threadmasked, NULL);if (rc != 0){printf("%d, %s\n", rc, strerror(rc));return -1;}}sleep(3);printf("Send a signal to masked and unmasked threads\n");for(i=0; i<NUMTHREADS; ++i){rc = pthread_kill(threads[i], SIGALRM);rc = pthread_kill(maskedthreads[i], SIGALRM);}printf("Wait for masked and unmasked threads to complete\n");for(i=0; i<NUMTHREADS; ++i) {rc = pthread_join(threads[i], NULL);rc = pthread_join(maskedthreads[i], NULL);}printf("Main completed\n");return 0;}void sighand(int signo){pthread_t tid = pthread_self();printf("Thread %lu in signal handler\n",tid);return;}程序返回：Enter Testcase - ./pthread_sigmask_testSet up the alarm handler for the processCreate masked and unmasked threadsThread 3086597040 enteredMasked thread 3076107184 enteredThread 3065617328 enteredMasked thread 3055127472 enteredThread 3044637616 enteredMasked thread 3034147760 enteredSend a signal to masked and unmasked threadsWait for masked and unmasked threads to completeThread 3086597040 in signal handlerThread 3086597040 did not get expected results! rc=27Thread 3065617328 in signal handlerThread 3065617328 did not get expected results! rc=27Thread 3044637616 in signal handlerThread 3044637616 did not get expected results! rc=27Masked thread 3076107184 completed masked workMasked thread 3055127472 completed masked workMasked thread 3034147760 completed masked workMain completed