操作系统-jyy-5 多处理器编程

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       #include <pthread.h>

       int pthread_join(pthread_t thread, void **retval);

       Compile and link with -pthread.

       The pthread_join() function waits for the thread specified by
       thread to terminate.  If that thread has already terminated, then
       pthread_join() returns immediately.  The thread specified by
       thread must be joinable.

       If retval is not NULL, then pthread_join() copies the exit status
       of the target thread (i.e., the value that the target thread
       supplied to pthread_exit(3)) into the location pointed to by
       retval.  If the target thread was canceled, then PTHREAD_CANCELED
       is placed in the location pointed to by retval.

       If multiple threads simultaneously try to join with the same
       thread, the results are undefined.  If the thread calling
       pthread_join() is canceled, then the target thread will remain
       joinable (i.e., it will not be detached).

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#include "thread.h"
#define N 100000000
long sum = 0;
void Tsum() {
  for (int i = 0; i < N; i++) {
    //sum++;
    asm volatile(
        "incq %0" : "+m"(sum)
    );
  }
}
int main() {
  create(Tsum);
  create(Tsum);
  join();
  printf("sum = %ld\n", sum);
}

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int x = 0, y = 0;

void T1() {
  x = 1;  // Store(x)
  printf("%d", y);  // Load(y)
}

void T2() {
  y = 1;  // Store(y)
  printf("%d", x); // Load(x)
}

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$ ./a.out | head -n 1000000 |sort |uniq -c
 902562 0 0 
  92944 0 1 
   4461 1 0 
     33 1 1