Mailing Lists: Apple Mailing Lists
Image of Mac OS face in stamp
 
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Problems with open() and close()

Hi all, first time poster to this list, hope that this is right list to post to...

I've adapted some code to my own uses (shown below) but have run into an odd problem, and I'm hoping that someone can explain what is going on to me. As a part of my open_TTY_OSX() function, I call ioctl (context->fileDescriptor, TIOCEXCL), which prevents any non-root program from opening the same device. Now this is where it gets odd for me. I am testing all this code using some unit tests that I wrote. The unit tests call open_TTY_OSX() and then balance the call with a call to close_TTY_OSX() on the same file descriptor. Originally, I did NOT have the ioctl(context->fileDescriptor, TIOCNXCL) call in close_TTY_OSX(), and the result was that if I tried to open the same device again, it would fail with EBUSY. So basically:

open_TTY_OSX("/dev/ttyp1", foo) // no problem
close_TTY_OSX(foo) // no problem
open_TTY_OSX("/dev/ttyp1, bar) // Fails with EBUSY

Well, I figured that this isn't that big a deal, I just let my process exit nicely, and the restart the debugging session, right? No good. The only way for me to make things play nice is to quit XCode, and even that doesn't seem to work 100% of the time. My question is why? When I close, I reset the attributes, and I close() the descriptor. That should make the blocking part go away, right? What am I doing wrong?

Oh, note that adjAssert() is a macro like assert(); I just hacked in some extra stuff that I needed, and didn't what the names conflicting.

Thanks for any help,
Cem Karan


#define ERROR_CLOSE_FD_TTY_OSX_PRIVATE (FD) \
{ \
struct stat myStat; \
perror (NULL); \
fflush (stderr); \
fflush (stdout); \
if (FD != -1) \
{ \
printf("Closing file descriptor"); \
fstat(FD, &myStat); \
close (FD); \
} \
}

boolean_t open_TTY_OSX(char *devicePath, OSX_TTYcontext context)
{
    size_t counter;

    adjAssert((devicePath != NULL) && (context != NULL));
    if ((devicePath == NULL) || (context == NULL))
        return false;

context->fileDescriptor = open(devicePath, O_RDWR | O_NOCTTY | O_NONBLOCK);
if (context->fileDescriptor == -1){
ERROR_CLOSE_FD_TTY_OSX_PRIVATE(context->fileDescriptor);
return false;
}

if (tcgetattr(context->fileDescriptor, &(context->original)) == -1) {
printf("Error getting tty attributes %s - %s(%d).\n",
devicePath, strerror(errno), errno);
ERROR_CLOSE_FD_TTY_OSX_PRIVATE(context->fileDescriptor);
return false;
}

memcpy(&(context->current), &(context->original), sizeof(struct termios));

    if (ioctl(context->fileDescriptor, TIOCEXCL) == -1) {
        ERROR_CLOSE_FD_TTY_OSX_PRIVATE(context->fileDescriptor);
        return false;
    }

    if (fcntl(context->fileDescriptor, F_SETFL, 0) == -1) {
        ERROR_CLOSE_FD_TTY_OSX_PRIVATE(context->fileDescriptor);
        return false;
    }

    if (fcntl(context->fileDescriptor, F_NOCACHE, 1) == -1) {
        ERROR_CLOSE_FD_TTY_OSX_PRIVATE(context->fileDescriptor);
        return false;
    }

    for (counter = 0; counter < NCCS; counter++)
        (context->current).c_cc[counter] = _POSIX_VDISABLE;

    cfmakeraw(&(context->current));

    (context->current).c_cc[VMIN]   = 1;
    (context->current).c_cc[VTIME]  = 1;
    cfsetspeed(&(context->current), B57600); 	/* Set 57600 baud */

    (context->current).c_cflag |= (CS8 | CREAD | CLOCAL);

if (tcsetattr(context->fileDescriptor, TCSANOW, &(context- >current)) == -1) {
ERROR_CLOSE_FD_TTY_OSX_PRIVATE(context->fileDescriptor);
return false;
}

    return true;
}

void close_TTY_OSX(OSX_TTYcontext context)
{
    int result;
    adjAssert(context != NULL);

    if (tcdrain(context->fileDescriptor) == -1) {
        printf("Error waiting for drain - %s(%d).\n",
            strerror(errno), errno);
    }

    if (ioctl(context->fileDescriptor, TIOCNXCL) == -1) {
        ERROR_CLOSE_FD_TTY_OSX_PRIVATE(context->fileDescriptor);
    }

if (tcsetattr(context->fileDescriptor, TCSANOW, &(context- >original)) == -1) {
printf("Error resetting tty attributes - %s(%d).\n",
strerror(errno), errno);
}

    result = close(context->fileDescriptor);
    if (result != 0)
        perror(NULL);
}

_______________________________________________
Do not post admin requests to the list. They will be ignored.
Darwin-dev mailing list      (email@hidden)
Help/Unsubscribe/Update your Subscription:
http://lists.apple.com/mailman/options/darwin-dev/email@hidden

This email sent to email@hidden


Visit the Apple Store online or at retail locations.
1-800-MY-APPLE

Contact Apple | Terms of Use | Privacy Policy

Copyright © 2007 Apple Inc. All rights reserved.