[LCP] Multi threading programming

[Robert Wuest]

wrap accesses to the global thing in a mutex:

#include <pthread.h>
static pthread_mutex_t counter_mutex = PTHREAD_MUTEX_INITIALIZER;
int my_global_counter;


then, to access my_gloab_int, use sequences like:

   pthread_mutex_lock(&counter_mutex);
   my_global_counter++;
   pthread_mutex_unlock(&counter_mutex);

Don't sleep with the mutex locked.

Compile with -pthread as one of your flags.

Robert

On Thu, 2009-02-19 at 13:21 -0900, Christopher Howard wrote:
> I'm am entirely unexperienced at multi threaded programming, but am about 
> to try and figure it out. For one of my programs I wanted to create a 
> simple "internal counter" function which which sleeps for 1000 
> milliseconds, then increments a global variable which other functions can 
> read. (I know this doesn't work as an accurate clock, but that is okay.)
> 
> My question: Does the global variable have to be some kind of atomic 
> variable? Will this still work correctly if it is an int or a long int? I 
> read something on the Internet about locking variables... does that apply 
> here?
> 
> Any (simple) examples would also be appreciated. Thank you in advance.
>