linuxthreads/tst-context.c

   1 #include <errno.h>
   2 #include <error.h>
   3 #include <pthread.h>
   4 #include <stdio.h>
   5 #include <stdlib.h>
   6 #include <ucontext.h>
   7
   8 #include "pt-machine.h"
   9
  10
  11 #define N       4
  12
  13 #ifdef FLOATING_STACKS
  14 static char stacks[N][8192];
  15 static ucontext_t ctx[N][2];
  16 static volatile int failures;
  17
  18 static void
  19 fct (long int n)
  20 {
  21   /* Just to use the thread local descriptor.  */
  22   printf ("%ld: in %s now\n", n, __FUNCTION__);
  23   errno = 0;
  24 }
  25
  26 static void *
  27 threadfct (void *arg)
  28 {
  29   int n = (int) (long int) arg;
  30
  31   if (getcontext (&ctx[n][1]) != 0)
  32     {
  33       printf ("%d: cannot get context: %m\n", n);
  34       exit (1);
  35     }
  36
  37   printf ("%d: %s: before makecontext\n", n, __FUNCTION__);
  38
  39   ctx[n][1].uc_stack.ss_sp = stacks[n];
  40   ctx[n][1].uc_stack.ss_size = 8192;
  41   ctx[n][1].uc_link = &ctx[n][0];
  42   makecontext (&ctx[n][1], (void (*) (void)) fct, 1, (long int) n);
  43
  44   printf ("%d: %s: before swapcontext\n", n, __FUNCTION__);
  45
  46   if (swapcontext (&ctx[n][0], &ctx[n][1]) != 0)
  47     {
  48       ++failures;
  49       printf ("%d: %s: swapcontext failed\n", n, __FUNCTION__);
  50     }
  51   else
  52     printf ("%d: back in %s\n", n, __FUNCTION__);
  53
  54   return NULL;
  55 }
  56 #endif
  57
  58
  59 static volatile int global;
  60
  61 int
  62 main (void)
  63 {
  64 #ifndef FLOATING_STACKS
  65   puts ("not supported");
  66   return 0;
  67 #else
  68   int n;
  69   pthread_t th[N];
  70   ucontext_t mctx;
  71
  72   puts ("making contexts");
  73   if (getcontext (&mctx) != 0)
  74     {
  75       if (errno == ENOSYS)
  76         {
  77           puts ("context handling not supported");
  78           exit (0);
  79         }
  80
  81       printf ("%s: getcontext: %m\n", __FUNCTION__);
  82       exit (1);
  83     }
  84
  85   /* Play some tricks with this context.  */
  86   if (++global == 1)
  87     if (setcontext (&mctx) != 0)
  88       {
  89         printf ("%s: setcontext: %m\n", __FUNCTION__);
  90         exit (1);
  91       }
  92   if (global != 2)
  93     {
  94       printf ("%s: 'global' not incremented twice\n", __FUNCTION__);
  95       exit (1);
  96     }
  97
  98   for (n = 0; n < N; ++n)
  99     if (pthread_create (&th[n], NULL, threadfct, (void *) n) != 0)
 100       error (EXIT_FAILURE, errno, "cannot create all threads");
 101
 102   for (n = 0; n < N; ++n)
 103     pthread_join (th[n], NULL);
 104
 105   return failures;
 106 #endif
 107 }