How to Kill a waiting pthread - multithreading

Question

Have a pthread that sleeps while waiting on a condition variable. I use a boolean in the outer while loop to keep it running. The problem I seem to have is when I change this variable the thread does not die.
I took a look in instruments and if I start a thread , tell it to die, then start a new one my thread count is 2 not 1.
How can I properly destroy this thread when I want to?
int worktodo=0;
BOOL runthread=NO;
pthread_cond_t cond=PTHREAD_COND_INITIALIZER;
pthread_mutex_t mutex=PTHREAD_MUTEX_INITIALIZER;
void *threadfunc(void *parm)
{
int rc;
while(runthread==YES)
{
rc=pthread_mutex_lock(&mutex);
while(!worktodo)
{
printf("thtread blocked\n");
rc=pthread_cond_wait(&cond, &mutex);
}
printf("thtread awake.... doing work\n");
// doing work
worktodo=0;
rc=pthread_mutex_unlock(&mutex);
}
// never reaches here!!
pthread_detach(NULL);
}
void makeThread()
{
pthread_attr_t attr;
int returnVal;
returnVal = pthread_attr_init(&attr);
assert(!returnVal);
runthread=YES;
returnVal = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
assert(!returnVal);
int threadError = pthread_create(&str->thread, &attr, &threadfunc, NULL);
returnVal = pthread_attr_destroy(&attr);
assert(!returnVal);
if (threadError != 0)
{
// Report an error.
}
}
void wakethread()
{
pthread_mutex_lock(&mutex);
worktodo=1;
pthread_cond_signal(&cond);
pthread_mutex_unlock(&mutex);
}
void killthread
{
runthread=NO;
}

Answer 1

thiton was correct. I couldnt kill the thread while it was blocked. Theres probably a better way to do this but the solution that worked for me was to set runthread to false then wake the thread.
void killthread
{
runthread=NO;
pthread_mutex_lock(&mutex);
worktodo=1;
pthread_cond_signal(&cond);
pthread_mutex_unlock(&mutex);
}

Answer 2

You initialize runthread to NO and compare it to YES. The thread should never reach the inside of its
while(runthread==YES)
loop. Besides, when the thread waits for work, killthread will not wake it up and runthread will stay in its work-waiting loop.