semaphore related - smtctl use IPC_RMID failed with Invalid argument

Question

If I do not define LINUX_ENV macro,everything goes well(especially,the IPC_RMID cmd return 0). but if I define LINUX_ENV(I am running on linux system-ubuntu10.04),the last semctl's IPC_RMID cmd return EINVAL,and says Invalid argument, i.e. the semaphore is not removed. it seems earlier semctl SEM_INFO cmd causes later IPC_RMID cmd return Invalid argument on linux system Where goes wrong in my code?Can anyone help me with this.Thanks in advance.

#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
#include <stdio.h>
#include <stdlib.h>
#include <time.h>

//#define LINUX_ENV

#ifdef LINUX_ENV
#define _GNU_SOURCE
#endif

union semun{
    int val;
    struct semid_ds *buf;
    unsigned short int *array;
    struct seminfo *__buf;
};

int main(int argc,char* argv[])
{
    key_t key;
    int semid;
    int nsems;
    int proj_id;

    struct semid_ds semid_ds_buf;
    union semun semun_buf;
    struct seminfo* sem_info;

    proj_id=rand();
    key=ftok(argv[0],proj_id);
    nsems=2;
    semid=semget(key,nsems,IPC_CREAT|IPC_EXCL|0666);
    if(semid==-1)
    {
        perror("semget failed");
        return -1;

    }else
    {
        printf("key(%s,%d) semaphore id:%d\n",argv[0],proj_id,semid);
    }
    semun_buf.buf=&semid_ds_buf;
    //nsems is ignored
    semctl(semid,0,IPC_STAT,&semid_ds_buf);

    printf("current number of semaphores:%lu\n",semid_ds_buf.sem_nsems);

#ifdef LINUX_ENV
    if(semctl(semid,0,SEM_INFO,&semun_buf)==-1)
    {
        printf("semctl SEM_INFO failed");
        return -2;
    }

    sem_info=(struct seminfo*)(&semid_ds_buf);
    printf("max entries in semaphore map:%d\n",sem_info->semmap);

#endif
    if(semctl(semid,0,IPC_RMID,0)==-1)
    {
        perror("semctl IPC-RMID failed");
        return -3;
    }
    return 0;
}

Answer 1

the SEM_INFO call returns the seminfo struct, defined as follows:

struct  seminfo {
    int semmap;  /* # of entries in semaphore map;
                 unused */
    int semmni;  /* Max. # of semaphore sets */
    int semmns;  /* Max. # of semaphores in all
                 semaphore sets */
    int semmnu;  /* System-wide max. # of undo
                 structures; unused */
    int semmsl;  /* Max. # of semaphores in a set */
    int semopm;  /* Max. # of operations for semop() */
    int semume;  /* Max. # of undo entries per
                 process; unused */
    int semusz;  /* size of struct sem_undo */
    int semvmx;  /* Maximum semaphore value */
    int semaem;  /* Max. value that can be recorded for
                 semaphore adjustment (SEM_UNDO) */
};

set the return buffer to the above structure and try again. hope it helps. (i couldn't recreate your problem using the above code on a RHEL5.4 system though.)

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