Pthreads

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Pthreads

• include ltpthread.hgt
• pthread_t tid //thread id.
• pthread_attr_t attr
• void sleeping(void ) / thread routine /
• main()
• int time 2
• pthread_create(tid, NULL, sleeping, time)
• void sleeping(int sleep_time)
• printf(thread sleeping for d secs\n,
  sleep_time)

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Pthreads

• Problem When main exits the process exits.
• main()
• int time 2
• pthread_create(tid, NULL, sleeping, time)
• pthread_join(tid, void NULL)
• void sleeping(int sleep_time)
• printf(thread sleeping for d secs\n,
  sleep_time)

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• pthread_t tids10
• main()
• for (j 0 j lt 10 j)
• pthread_create(tidsi, NULL, sleeping, time)
  
• for(j 0 j lt 10 j)
• pthread_join(tidi, NULL)

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All theads share global variables file
descriptors static variables within creating
function. Local variables are private to each
thread. void sleeping(int sleep_time)
static int tootoo 10 printf(thread
sleeping for d secs\n, sleep_time)
tootoo //will have final value of 20.
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Synchronization Constructs mutex and condition
variables Main() pthread_mutex_t my_mute
//initialize pthread_mutex_init(my_mute,
NULL) pthread_mutex_lock(my_mute)//blocks
caller till mutex unlocked // by owner
-critical code pthread_mutex_unlock(my_mute)
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You can also test a mutex to see if it is
available pthread_mutex_trylock(my_mute) If
multiple threads blocked on mutex, one will be
chosen Based on the scheduling algorithm.
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Condition variable allows threads to wait on some
event and resume when the event has
occurred. Condition variable associated with a
mutex! Thread must acquire mutex before calling
pthread_cond_wait(). pthread_mutex_t my_mute
pthread_cond_t condalisa pthread_mutex_init(m
ymute) thread_cond_init(condalisa)
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pthread_mutex_lock(my_mute) pthread_cond_wait(
condalisa, my_mute) This call to wait
atomically checks the condition and blocks (if
necessary). If the thread blocks, the mutex is
automatically released. Woken up with call to
pthread_cond_signal pthread_cond_signal(cond
alisa) //wakes up one //thread. pthread_co
nd_broadcast (condalisa) //wakes up all
threads