linuxthreads/tst-context.c

   1 /* Ack, a hack!  We need to get the proper definition, or lack thereof,
   2    for FLOATING_STACKS.  But when !IS_IN_libpthread, this can get defined
   3    incidentally by <tls.h>.  So kludge around it.  */
   4
   5 #define IS_IN_libpthread
   6 #include <tls.h>
   7 #undef IS_IN_libpthread
   8 #undef USE___THREAD
   9
  10 #include <errno.h>
  11 #include <error.h>
  12 #include <pthread.h>
  13 #include <stdio.h>
  14 #include <stdlib.h>
  15 #include <ucontext.h>
  16
  17
  18 #define N       4
  19
  20 #ifdef FLOATING_STACKS
  21 static char stacks[N][8192];
  22 static ucontext_t ctx[N][2];
  23 static volatile int failures;
  24
  25 static void
  26 fct (long int n)
  27 {
  28   /* Just to use the thread local descriptor.  */
  29   printf ("%ld: in %s now\n", n, __FUNCTION__);
  30   errno = 0;
  31 }
  32
  33 static void *
  34 threadfct (void *arg)
  35 {
  36   int n = (int) (long int) arg;
  37
  38   if (getcontext (&ctx[n][1]) != 0)
  39     {
  40       printf ("%d: cannot get context: %m\n", n);
  41       exit (1);
  42     }
  43
  44   printf ("%d: %s: before makecontext\n", n, __FUNCTION__);
  45
  46   ctx[n][1].uc_stack.ss_sp = stacks[n];
  47   ctx[n][1].uc_stack.ss_size = 8192;
  48   ctx[n][1].uc_link = &ctx[n][0];
  49   makecontext (&ctx[n][1], (void (*) (void)) fct, 1, (long int) n);
  50
  51   printf ("%d: %s: before swapcontext\n", n, __FUNCTION__);
  52
  53   if (swapcontext (&ctx[n][0], &ctx[n][1]) != 0)
  54     {
  55       ++failures;
  56       printf ("%d: %s: swapcontext failed\n", n, __FUNCTION__);
  57     }
  58   else
  59     printf ("%d: back in %s\n", n, __FUNCTION__);
  60
  61   return NULL;
  62 }
  63 #endif
  64
  65
  66 #ifdef FLOATING_STACKS
  67 static volatile int global;
  68 #endif
  69
  70 int
  71 main (void)
  72 {
  73 #ifndef FLOATING_STACKS
  74   puts ("not supported");
  75   return 0;
  76 #else
  77   int n;
  78   pthread_t th[N];
  79   ucontext_t mctx;
  80
  81   puts ("making contexts");
  82   if (getcontext (&mctx) != 0)
  83     {
  84       if (errno == ENOSYS)
  85         {
  86           puts ("context handling not supported");
  87           exit (0);
  88         }
  89
  90       printf ("%s: getcontext: %m\n", __FUNCTION__);
  91       exit (1);
  92     }
  93
  94   /* Play some tricks with this context.  */
  95   if (++global == 1)
  96     if (setcontext (&mctx) != 0)
  97       {
  98         printf ("%s: setcontext: %m\n", __FUNCTION__);
  99         exit (1);
 100       }
 101   if (global != 2)
 102     {
 103       printf ("%s: 'global' not incremented twice\n", __FUNCTION__);
 104       exit (1);
 105     }
 106
 107   for (n = 0; n < N; ++n)
 108     if (pthread_create (&th[n], NULL, threadfct, (void *) (long int) n) != 0)
 109       error (EXIT_FAILURE, errno, "cannot create all threads");
 110
 111   for (n = 0; n < N; ++n)
 112     pthread_join (th[n], NULL);
 113
 114   return failures;
 115 #endif
 116 }