PROBLEM - Signals not handled while waiting on semphores

[Gabi Davar]

Hi,

I'm unable to receive signals while waiting on semaphores. The following 
short program illustrates the problem. Sending SIGUSR1 when in semop 
does not result in "sig handler!!!" print.

Attached strace dump & cygcheck.

Anyone can help me out is making this work or explain what's going on?

======================================================================
#include <signal.h>
#include <stdio.h>
#include <time.h>
#include <string.h>
#include <unistd.h>
#include <sys/fcntl.h>
#include <sys/sem.h>
#include <errno.h>

void GIntHandler( int bogus )
{
    printf( "sig handler!!!\n" );
}


#define PERMS (S_IRUSR | S_IWUSR | S_IRGRP | S_IWGRP | S_IROTH | S_IWOTH)

int main()
{
    struct sigaction gintact;
    int semid;
    union semun {
        int val;
        struct semid_ds *buf;
        unsigned short *array;
    } arg;
    
    gintact.sa_handler = &GIntHandler;
    gintact.sa_flags = SA_RESTART;
    
    if (sigemptyset( &gintact.sa_mask ) < 0) {
          perror("Failed to initialize the signal mask");
          return 1;
    }

    if (sigaction( SIGUSR1, &gintact, NULL ) < 0) {
        perror("Failed to install the handler");
        return 1;
    }
    
    if ((semid = semget( (key_t)1997, 1, PERMS | IPC_CREAT )) == -1 ) {
        perror( "Failed to create sempahore" );
        return 1;
    }
    
    arg.val = 0;
    
    if (semctl(semid, 0, SETVAL, arg) < 0) {
        perror( "Failed to initialize smeaphore" );
        return 1;
    }

    {
        struct sembuf op;

        op.sem_num = (short)0;
        op.sem_op = (short)-1;
        op.sem_flg = (short)0;
        if (semop( semid, &op, 1 ) < 0) {
            perror( "failed to perform action on sempatore" );
            return 1;
        }
    }

    return 0;
}


Gabi Davar
Emblaze Semiconductor LTD.
Phone:  +972 9 7699566
Email:  gabid@emblazesemi.com
Web:    www.EmblazeSemi.com
 

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