Question

我曾尝试在64位Ubuntu中使用 setjmp / longjmp ，但它不能正常工作，而它在32位Ubuntu中正常工作。任何想法，发生了什么。以下是代码，我试图执行。

在64位上，它会在longjmp之后返回时挂起。在维基百科关于setcontext的文章中，它表示它与64位无法正常工作。我们在 setjmp 时遇到同样的问题吗？事实上，我试图使用 setjmp ，以避免 setcontext 的问题，但它似乎在64位上有相同的问题。

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include <string>
#include <setjmp.h>

#define NOFTHREADS 2

#define DATASIZE        500
#define SETSIZE         (DATASIZE / NOFTHREADS)  

int data[DATASIZE];
pthread_mutex_t sumMutex;
pthread_mutex_t prodMutex;
int sum;
double prod;
static jmp_buf buf;
int jmp_onced[NOFTHREADS+1];

#define lock pthread_mutex_lock
#define unlock pthread_mutex_unlock

void *SumThread( void *pParam )
{
  unsigned int tid = *((unsigned int*)(pParam));
  int si = tid * SETSIZE;
  int i, j, oi, local_sum;
  double local_prod;
  pthread_attr_t attr;

  if ( setjmp(buf) ) 
    printf( "%d: tid %u back! <<<<<<<<<\n", getpid(), tid );
  if ( jmp_onced[tid] )
    goto end_this;

  printf( "%d: >>>>>>>>>>>>> tid %u, starting <<<<<<<<<<<<\n\n", getpid(), tid );

  for( oi = 0; oi < 5; oi++ )
  {
    local_sum = 0;
    local_prod = 1.0;
    for( i = si; i < (si+SETSIZE); i++ )
    {
      local_sum = local_sum + data[i];
      if ( data[i ] )
      local_prod *= 0.005 * data[i];
    }

    lock( &sumMutex );
    sum += local_sum;
    unlock( &sumMutex );

    lock( &prodMutex );
    prod *= local_prod;
    unlock( &prodMutex );
  }

  printf( "%d: !!!!!!!!!!!!!!tid %u done!!!!!!!!!!!!!!\n\n", getpid(), tid );
  jmp_onced[tid] = 1;
  longjmp( buf, 1 );

end_this:
  printf( "%d: ****** tid %u is exiting! ******\n", getpid(), tid ); 
  return 0;
}

void real_main()
{
  pthread_t hThread[NOFTHREADS];
  int index[NOFTHREADS];
  int i, pid, err;
  time_t t1 = time(NULL);

  printf( "%d: Inside real_main, primary thread = %lx!\n", getpid(), pthread_self() );
  for( i = 0; i < NOFTHREADS; i++ )
  {
      index[i] = i;
      pthread_create( &hThread[i], NULL, SumThread, &index[i] ); 
  }
  for( i = 0; i < NOFTHREADS; i++ )
      pthread_join( hThread[i], NULL );

  printf( "Sum of numbers from 1 to %d is %d\n", DATASIZE, sum ); 
  printf( "Prod of numbers from 1 to %d is %g\n", DATASIZE, prod );
  printf( "\n\n[[[[[ %d(child of %d): Time taken = %lu seconds ]]]]]\n\n", getpid(), getppid(), time(NULL) - t1 );
}

int main(int argc, char **argv)
{
  int pid, i, err;

  printf( "size of long is %d\n", sizeof( long ) );

  sumMutex = PTHREAD_MUTEX_INITIALIZER;
  prodMutex = PTHREAD_MUTEX_INITIALIZER;
  printf( "pid = %d, @sumMutex = %lx, @prodMutex = %lx\n", getpid(), (long)&sumMutex, (long)&prodMutex );   

  for( i = 0; i < DATASIZE; i++ )
    data[i] = i+1;

  switch(pid = fork())
  {
  case -1:
    printf("fork failed");
    break;
  case 0: // Child
    printf( "Child pid() = %d\n", getpid() );
    real_main();
    break;
  default:// Leader
    printf( "Parent pid() = %d\n", getpid() );
    real_main();
  }

  printf( "getppid() = %d, getpid() = %d\n", getppid(), getpid() );
  return 0;
}

Answer 1

您需要为每个帖子使用单独的jmp_buf。目前你正在重复使用同一个。

Answer 2

如果您没有声明本地变量volatile，并且在调用setjmp()后更改了这些变量，则在致电longjmp()时无法保证保留这些变量。

（C99标准中的7.13.2.1/3。）

但这似乎不适用于此，因为si和tid不会更改。

64位的setjmp / longjmp

2 个答案: