如何从linux命令提示符下删除/释放命名信号量

Question

我有一个代码如下。它在访问信号量时崩溃；命名信号量"；崩溃后，我无法从命令提示符中删除。如何使用命令提示符实用程序删除它们？该代码试图创建Rock，Paper，Scissors游戏，该游戏可以从两个生产者(玩家(命令提示符和一个消费者(结果(命令提示符运行。我也希望您能提出修改/纠正/改进代码的建议。

//compiled by executing --> gcc -pthread logic.c  -lrt
#include <stdio.h>
#include <sys/shm.h>
#include <semaphore.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <string.h>
#include <sys/fcntl.h>
#include <sys/mman.h>
//don't need an exec call just based on paramters run the processes
typedef struct sync_tools
{
int pid;
void* shm_ptr;
sem_t* sem_array[2];
} sync_tools;
void producer(void * ctx)
{
char choice;
sync_tools *ctxt=(sync_tools*)ctx;
while(1)
{
printf ("Enter the following for input n");
printf ("R. Rockn");
printf ("P. Papern");
printf ("S. Scissorsn");
scanf ("%c",&choice);

if (ctxt->pid==1)
{    
printf ("Process1n");
sem_wait(ctxt->sem_array[0]);
sprintf((char*) ctxt->shm_ptr, "%cn", choice);
sem_post(ctxt->sem_array[0]);
printf ("Process1n");
}
else
{
printf ("Process2n");
sem_wait(ctxt->sem_array[1]);
sprintf((char*) (ctxt->shm_ptr+1), "%cn", choice);
sem_post(ctxt->sem_array[1]);
}
}
}
//need 2 semphores for sync
void consumer(void *ctx)
{
sync_tools *ctxt=(sync_tools*)ctx;
char data[2]={0x00};
int flag=1;
while(1)
{
sem_wait(ctxt->sem_array[0]);
sem_wait(ctxt->sem_array[1]);
scanf ((char *) ctxt->shm_ptr, "%c", &data[0]);
scanf ((char *) (ctxt->shm_ptr+1), "%c", &data[1]);
switch(data[0])
{
case 'R':
case 'r':
if ((data[1] =='p')|| (data[1]=='P'));
flag=0;
break;
case'P':
case'p':    
if ((data[1] =='s')|| (data[1]=='S'));
flag=0;
break;
case 's':
case'S':
if ((data[1] =='R')|| (data[1]=='R'));
flag=0;
break;
}   
if (flag)
printf("Process 1 wins n");
else
printf("Process 2 wins n");
sem_post(ctxt->sem_array[0]);
sem_post(ctxt->sem_array[1]);
}
}
int main (int argc, char* argv[])
{
char choice;
int SIZE=4096;
char *name="SHM_WQ";
sync_tools cntxt={}; //initialize without memset
//calling sem_open as I want a named semaphore which is not locally available by copy like in forked processes.
cntxt.sem_array[0]= sem_open ("P1C", O_CREAT | O_EXCL, 0644, 1); 
cntxt.sem_array[1]= sem_open ("P2C", O_CREAT | O_EXCL, 0644, 1); 
/* shared memory file descriptor */
int shm_fd;
/* pointer to shared memory object */
void* ptr;
/* create the shared memory object */
shm_fd = shm_open(name, O_CREAT | O_RDWR, 0666);
/* configure the size of the shared memory object */
ftruncate(shm_fd, SIZE);
/* memory map the shared memory object */
ptr = mmap(0, SIZE, PROT_WRITE, MAP_SHARED, shm_fd, 0); //sys/mman.h 
cntxt.shm_ptr=ptr;
//pass the shared memory and semaphores to all the threads and spawn them
if(strcmp(argv[1], "p1") == 0)
cntxt.pid=1;
else if (strcmp(argv[1], "p2") ==0)
cntxt.pid=2;
else if (strcmp(argv[1], "c") ==0)
cntxt.pid=3;//don't care
producer(&cntxt);
consumer(&cntxt);
}

Answer 1

修改我的代码如下：

cntxt.sem_array[0] = sem_open("P1C", 0);
cntxt.sem_array[1] = sem_open("P2C", 0);
if (cntxt.sem_array[0] == NULL)
{
cntxt.sem_array[0]= sem_open ("P1C", O_CREAT | O_EXCL, 0644, 2);
}
if (cntxt.sem_array[1] == NULL)
{
cntxt.sem_array[1]= sem_open ("P2C", O_CREAT | O_EXCL, 0644, 2);
}
if ((cntxt.sem_array[0] == NULL) || (cntxt.sem_array[1] == NULL))
printf("SEM_OPEN ERROR");

正如评论中提到的，创建了一个小实用程序，它接受semname并将其从内核中取消链接。