[TriLUG] Why do File IO event seem to be out-of-order in strace?

[Igor Partola via TriLUG]

Looks to me like you are doing fork() incorrectly:

 if(childPID >= 0) // fork was successful
    {
        if(childPID == 0) // child process
        {

This code after the above statement will run for both parent and child.
Since you are doing this in a loop the second process you fork will inherit
the parent's lock.

The correct way to write this would be like so:

childPID = fork();

if (childPID < 0) {
    puts("Could not fork!");
    abort(1);
}

if (childPID == 0) {
    // Do the lock test.
}

if (childPID > 0) {
     // Spawn more children or wait on existing children to exit.
}


For your test, you don't need to fork(). Simply have a program that does
the locking with a 10 second sleep before unlocking it. Fire off this same
program twice and watch the second one take longer than 10 seconds while it
waits for the lock.

Igor