strace-threads.patch

   1 diff -durN strace-4.4.orig/strace.c strace-4.4/strace.c
   2 --- strace-4.4.orig/strace.c    Fri Aug  3 13:43:35 2001
   3 +++ strace-4.4/strace.c Thu Jul  4 10:41:55 2002
   4 @@ -993,58 +993,110 @@
   5  #ifdef LINUX
   6         /*
   7          * Linux wrongly insists the child be stopped
   8 -        * before detaching.  Arghh.  We go through hoops
   9 -        * to make a clean break of things.
  10 +        * before detaching.  This creates numerous headaches
  11 +        * as the process we are tracing may be running.
  12 +        *
  13 +        * First try to simply detach from the process; if it was
  14 +        * already stopped, this will succeed and we're done.
  15 +        *
  16 +        * Otherwise stop the process by sending it a SIGSTOP
  17 +        * signal.
  18 +        *
  19 +        * Once the process is stopped we have to make sure it
  20 +        * received the SIGSTOP (it may have received a SIGTRAP or
  21 +        * other signal).  If it did not receive the SIGSTOP,
  22 +        * restart the process and try again.
  23 +        *
  24 +        * Once stopped with a SIGSTOP, we can detach from the
  25 +        * process via PTRACE_DETACH.
  26 +        *
  27          */
  28 -#if defined(SPARC)
  29 -#undef PTRACE_DETACH
  30 -#define PTRACE_DETACH PTRACE_SUNDETACH
  31 -#endif
  32 +
  33         if ((error = ptrace(PTRACE_DETACH, tcp->pid, (char *) 1, sig)) == 0) {
  34                 /* On a clear day, you can see forever. */
  35 -       }
  36 -       else if (errno != ESRCH) {
  37 -               /* Shouldn't happen. */
  38 -               perror("detach: ptrace(PTRACE_DETACH, ...)");
  39 -       }
  40 -       else if (kill(tcp->pid, 0) < 0) {
  41 -               if (errno != ESRCH)
  42 -                       perror("detach: checking sanity");
  43 -       }
  44 -       else if (kill(tcp->pid, SIGSTOP) < 0) {
  45 -               if (errno != ESRCH)
  46 -                       perror("detach: stopping child");
  47 -       }
  48 -       else {
  49 +       } else {
  50 +
  51                 for (;;) {
  52 -                       if (waitpid(tcp->pid, &status, 0) < 0) {
  53 -                               if (errno != ECHILD)
  54 +                       if (kill(tcp->pid, 0) < 0) {
  55 +                               if (errno != ESRCH)
  56 +                                       perror("detach: checking sanity");
  57 +                       }
  58 +                       else if (kill(tcp->pid, SIGSTOP) < 0) {
  59 +                               if (errno != ESRCH)
  60 +                               perror("detach: stopping child");
  61 +                       }
  62 +
  63 +                       /*
  64 +                       * At this point the child should be stopped.  Try to
  65 +                       * wait on it so we can get its stop status.  Use WNOHANG
  66 +                       * to avoid this wait hanging.
  67 +                       */
  68 +                       if (waitpid (tcp->pid, &status, (WUNTRACED | WNOHANG)) < 0) {
  69 +                               if (errno != ECHILD) {
  70                                         perror("detach: waiting");
  71 -                               break;
  72 +                               } else {
  73 +
  74 +                                       /*
  75 +                                       * Try again, this time with the __WCLONE
  76 +                                       * flag.  Note we may get notifications
  77 +                                       * for other processes/threads!
  78 +                                       */
  79 +                                       errno = 0;
  80 +                                       while (1) {
  81 +                                               int x;
  82 +
  83 +                                               x = waitpid (-1, &status, __WCLONE);
  84 +                                               if (x == tcp->pid || x < 0 || errno != 0)
  85 +                                                       break;
  86 +                                       }
  87 +                               }
  88 +
  89 +                               if (errno) {
  90 +                                       perror ("Unable to wait on inferior");
  91 +                                       return -1;
  92 +                               }
  93                         }
  94 +
  95 +                       /*
  96 +                       * At this point we have wait status for the
  97 +                       * inferior.  If it did not stop, then all
  98 +                       * bets are off.
  99 +                       */
 100                         if (!WIFSTOPPED(status)) {
 101                                 /* Au revoir, mon ami. */
 102                                 break;
 103                         }
 104 +
 105 +                       /*
 106 +                       * If the process/thread has stopped with a
 107 +                       * SIGSTOP, then we can continue and detach
 108 +                       * with PTRACE_DETACH.
 109 +                       */
 110                         if (WSTOPSIG(status) == SIGSTOP) {
 111                                 if ((error = ptrace(PTRACE_DETACH,
 112 -                                   tcp->pid, (char *) 1, sig)) < 0) {
 113 +                               tcp->pid, (char *) 1, sig)) < 0) {
 114                                         if (errno != ESRCH)
 115                                                 perror("detach: ptrace(PTRACE_DETACH, ...)");
 116                                         /* I died trying. */
 117                                 }
 118                                 break;
 119                         }
 120 +
 121 +                       /*
 122 +                       * The process/thread did not stop with a SIGSTOP,
 123 +                       * so let it continue and try again to stop it with
 124 +                       * a SIGSTOP.
 125 +                       */
 126                         if ((error = ptrace(PTRACE_CONT, tcp->pid, (char *) 1,
 127 -                           WSTOPSIG(status) == SIGTRAP ?
 128 -                           0 : WSTOPSIG(status))) < 0) {
 129 +                       WSTOPSIG(status) == SIGTRAP ?
 130 +                       0 : WSTOPSIG(status))) < 0) {
 131                                 if (errno != ESRCH)
 132                                         perror("detach: ptrace(PTRACE_CONT, ...)");
 133                                 break;
 134                         }
 135                 }
 136         }
 137 -#endif /* LINUX */
 138 +#endif
 139
 140  #if defined(SUNOS4)
 141         /* PTRACE_DETACH won't respect `sig' argument, so we post it here. */