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Full Discussion: Problem with signal handler and interrupted system call
Top Forums Programming Problem with signal handler and interrupted system call Post 302280302 by otheus on Monday 26th of January 2009 12:45:58 PM
Old 01-26-2009
Quote:
Code:
       retval = read(fd, &data, sizeof(unsigned long));
        if (retval == -1) {
            perror("read");
            exit(errno);
        }

That's your problem, more or less. If read() is interrupted by a system call, it returns -1, sets errno to EINTR. Your program itself does the perror and exiting, not read(). So just check if the return is -1 and errno != EINTR and restart the loop (for instance). You'll have to handle the logic for the ioctls and what not, too, or every now and then, your signal will interrupt the ioctl and exit.
 

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LEARN ABOUT ULTRIX

siginterrupt

siginterrupt(3) 					     Library Functions Manual						   siginterrupt(3)

Name
       siginterrupt - allow signals to interrupt system calls

Syntax
       siginterrupt(sig, flag)
       int sig, flag;

Description
       The  system call is used to change the system call restart behavior when a system call is interrupted by the specified signal.  If the flag
       is false (0), then system calls will be restarted if they are interrupted by the specified signal and no data  has  been  transferred  yet.
       System call restart is the default behavior on 4.2 BSD.

       If  the flag is true (1), then restarting of system calls is disabled.  If a system call is interrupted by the specified signal and no data
       has been transferred, the system call will return -1 with errno set to EINTR.  Interrupted system calls that have started transferring data
       will  return the amount of data actually transferred.  System call interrupt is the signal behavior found on 4.1 BSD and AT&T System V sys-
       tems.

       Note that the new signal handling semantics are not altered in any other way.  Most notably, signal handlers always remain installed  until
       explicitly  changed  by a subsequent call, and the signal mask operates as documented in Programs may switch between restartable and inter-
       ruptible system call operation as often as desired in the execution of a program.

       Issuing a call during the execution of a signal handler will cause the new action to take place on the next signal to be caught.

Environment
       This library routine uses an extension of the system call that is not available in ULTRIX 2.0 or earlier versions.  Hence it should not	be
       used if backward compatibility is needed.

Return Values
       A 0 value indicates that the call succeeded.  A -1 value indicates that an invalid signal number has been supplied.

See Also
       sigvec(2), sigblock(2), sigpause(2), sigsetmask(2)

4.3 Berkeley Distribution													   siginterrupt(3)
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