Subj : Re: Help me using pthreah!!! :) please...
To   : comp.programming.threads
From : ptjm
Date : Sat Jun 25 2005 02:42 pm

In article <6cbve.1351$h5.55369@news3.tin.it>,
tranky <NOSPAM@THANKY.YOU> wrote:

% I've this code of Reader-Writer Problem. I want that writer 2  starts N
% seconds
% after the execution of writer1.
% What i will do??
% I thing i will use the function pthread_kill e sigwait, but i don't know how
% to!

Don't use pthread_kill() for this. Use a condition variable to signal
state changes between threads. Writer 2 would do something like this

 pthread_mutex_lock(&mux);
 while (waiting_for_writer_one)
   pthread_cond_wait(&mux, &cv);
 waiting_for_writer_one = 0;
 pthread_mutex_unlock(&mux);

 sleep(N); /* for whatever reason */ 

Writer 1 would do this at the point it wants writer 2 to start sleeping:

 pthread_mutex_lock(&mux);
 waiting_for_writer_one = 1;
 pthread_mutex_unlock(&mux);
 pthread_cond_signal(&cv);

% (and if is possible can you say me how create a sixth thread that starts
% ever N second after the starting of the program?!?)

It could just sleep for N seconds. If the drift you get (after sleeping
for N seconds 10 times, N*10 + D seconds will have passed for some D > 0),
you could use clock_nanosleep

  struct timespec ts;
  clock_gettime(CLOCK_REALTIME, &ts):

  while (1) {
    ts.tv_sec += N;
    while (clock_nanosleep(CLOCK_REALTIME, TIMER_ABSTIME, &ts) == EINTR)
       ;

    do_whatever();
  }
-- 

Patrick TJ McPhee
North York  Canada
ptjm@interlog.com

.