Multi-threaded synchronization

Multi-threaded synchronization

One, what is synchronization

Multiple threads are executed in the specified order, which is thread synchronization.

1.1 Thread synchronization Mode one

Thread synchronization can be achieved by mutual exclusion lock, but the execution efficiency is lower (SYNC.C)

1#include <stdio.h>2#include <pthread.h>3#include <string.h>4 5 6pthread_t thread[2];7 intNumber =0; 8 pthread_mutex_t Mut;9 Ten  One voidStudenta () A { -     inti; -      for(i=0;i<5; i++) the     {   -Pthread_mutex_lock (&mut); -         //sweeping -number++; +         if(number>=5 ) -printf"student A has the finish his work! \ n");  +          APthread_mutex_unlock (&mut);  at         //rest for 1 seconds . -Sleep1); -     }  -     //Exit - Pthread_exit (NULL); - } in  - voidSTUDENTB () to {         +      while(1) -     {   thePthread_mutex_lock (&mut); *         if(number>=5)//judge whether a classmate has finished sweeping 5 times $         {   Panax Notoginseng             //perform a drag-and-drop -Number =0;  theprintf"student B has finish he work \ n"); +              APthread_mutex_unlock (&mut); the             //Exit +              Break;  -         }  $         Else $         {   -Pthread_mutex_unlock (&mut); -             //Sleep 2 seconds theSleep2);  -         }    Wuyi     } thePthread_exit (NULL);//Exit - } Wu  - intMain () About {    $     //Initialize Mutex lock -Pthread_mutex_init (&mut,null); -  -     //Create a classmate thread APthread_create (&thread[0],null,studenta,null); +      the     //Create a Class B thread -Pthread_create (&thread[1],null,studentb,null); $          the     //waiting for a classmate thread to end thePthread_join (thread[0],null); the      the     //wait for Class B thread to end -Pthread_join (thread[1],null); in          the     return 0; the}

1.2 thread synchronization mode two

Use of condition variables to increase CPU utilization (SYNC1.C)

1#include <stdio.h>2#include <pthread.h>3#include <string.h>4 5 6pthread_t thread[2];7 intNumber =0; 8 pthread_mutex_t Mut;9pthread_cond_t cond_ready=Pthread_cond_initializer;Ten  One voidStudenta () A { -     inti; -      for(i=0;i<5; i++) the     {   -Pthread_mutex_lock (&mut); -         //sweeping -number++; +         if(number>=5 ) -         { +printf"student A has the finish his work! \ n");  A              at             //Notify Class B -Pthread_cond_signal (&Cond_ready);  -         }     -Pthread_mutex_unlock (&mut);  -         //rest for 1 seconds . -Sleep1); in     }  -     //Exit to Pthread_exit (NULL); + } -  the voidSTUDENTB () * {         $ Panax NotoginsengPthread_mutex_lock (&mut); -     if(number<5) thePthread_cond_wait (&cond_ready, &mut);  +Number =0;  APthread_mutex_unlock (&mut); theprintf"student B has a finish his work! \ n");  +      -Pthread_exit (NULL);//Exit $ } $  - intMain () - {    the     //Initialize Mutex lock -Pthread_mutex_init (&mut,null);Wuyi  the     //Create a classmate thread -Pthread_create (&thread[0],null,studenta,null); Wu      -     //Create a Class B thread AboutPthread_create (&thread[1],null,studentb,null); $          -     //waiting for a classmate thread to end -Pthread_join (thread[0],null); -      A     //wait for Class B thread to end +Pthread_join (thread[1],null); the          -     return 0; $}

1.3 Item variables

Initialization

pthread_cond_t Cond_ready=pthread_cond_initializer;

Wait condition ripe:

Pthread_cond_wait (&cond_ready, &mut);

Set Condition Maturity:

Pthread_cond_signal (&cond_ready);

Multi-threaded synchronization