pkgs/by-name/gn/gnumake42/pselect.patch

   1 From b552b05251980f693c729e251f93f5225b400714 Mon Sep 17 00:00:00 2001
   2 From: Paul Smith <psmith@gnu.org>
   3 Date: Sat, 3 Jun 2017 16:20:51 -0400
   4 Subject: [SV 51159] Use a non-blocking read with pselect to avoid hangs.
   5
   6 * posixos.c (set_blocking): Set blocking on a file descriptor.
   7 (jobserver_setup): Set non-blocking on the jobserver read side.
   8 (jobserver_parse_auth): Ditto.
   9 (jobserver_acquire_all): Set blocking to avoid a busy-wait loop.
  10 (jobserver_acquire): If the non-blocking read() returns without
  11 taking a token then try again.
  12 ---
  13  posixos.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++-----------------
  14  1 file changed, 71 insertions(+), 26 deletions(-)
  15
  16 diff --git posixos.c posixos.c
  17 index e642d7f..dbafa51 100644
  18 --- posixos.c
  19 +++ posixos.c
  20 @@ -62,6 +62,24 @@ make_job_rfd (void)
  21  #endif
  22  }
  23
  24 +static void
  25 +set_blocking (int fd, int blocking)
  26 +{
  27 +  // If we're not using pselect() don't change the blocking
  28 +#ifdef HAVE_PSELECT
  29 +  int flags;
  30 +  EINTRLOOP (flags, fcntl (fd, F_GETFL));
  31 +  if (flags >= 0)
  32 +    {
  33 +      int r;
  34 +      flags = blocking ? (flags & ~O_NONBLOCK) : (flags | O_NONBLOCK);
  35 +      EINTRLOOP (r, fcntl (fd, F_SETFL, flags));
  36 +      if (r < 0)
  37 +        pfatal_with_name ("fcntl(O_NONBLOCK)");
  38 +    }
  39 +#endif
  40 +}
  41 +
  42  unsigned int
  43  jobserver_setup (int slots)
  44  {
  45 @@ -86,6 +104,9 @@ jobserver_setup (int slots)
  46          pfatal_with_name (_("init jobserver pipe"));
  47      }
  48
  49 +  /* When using pselect() we want the read to be non-blocking.  */
  50 +  set_blocking (job_fds[0], 0);
  51 +
  52    return 1;
  53  }
  54
  55 @@ -121,6 +142,9 @@ jobserver_parse_auth (const char *auth)
  56        return 0;
  57      }
  58
  59 +  /* When using pselect() we want the read to be non-blocking.  */
  60 +  set_blocking (job_fds[0], 0);
  61 +
  62    return 1;
  63  }
  64
  65 @@ -169,7 +193,10 @@ jobserver_acquire_all (void)
  66  {
  67    unsigned int tokens = 0;
  68
  69 -  /* Close the write side, so the read() won't hang.  */
  70 +  /* Use blocking reads to wait for all outstanding jobs.  */
  71 +  set_blocking (job_fds[0], 1);
  72 +
  73 +  /* Close the write side, so the read() won't hang forever.  */
  74    close (job_fds[1]);
  75    job_fds[1] = -1;
  76
  77 @@ -236,18 +263,12 @@ jobserver_pre_acquire (void)
  78  unsigned int
  79  jobserver_acquire (int timeout)
  80  {
  81 -  sigset_t empty;
  82 -  fd_set readfds;
  83    struct timespec spec;
  84    struct timespec *specp = NULL;
  85 -  int r;
  86 -  char intake;
  87 +  sigset_t empty;
  88
  89    sigemptyset (&empty);
  90
  91 -  FD_ZERO (&readfds);
  92 -  FD_SET (job_fds[0], &readfds);
  93 -
  94    if (timeout)
  95      {
  96        /* Alarm after one second (is this too granular?)  */
  97 @@ -256,28 +277,52 @@ jobserver_acquire (int timeout)
  98        specp = &spec;
  99      }
 100
 101 -  r = pselect (job_fds[0]+1, &readfds, NULL, NULL, specp, &empty);
 102 -
 103 -  if (r == -1)
 104 +  while (1)
 105      {
 106 -      /* Better be SIGCHLD.  */
 107 -      if (errno != EINTR)
 108 -        pfatal_with_name (_("pselect jobs pipe"));
 109 -      return 0;
 110 -    }
 111 +      fd_set readfds;
 112 +      int r;
 113 +      char intake;
 114
 115 -  if (r == 0)
 116 -    /* Timeout.  */
 117 -    return 0;
 118 +      FD_ZERO (&readfds);
 119 +      FD_SET (job_fds[0], &readfds);
 120
 121 -  /* The read FD is ready: read it!  */
 122 -  EINTRLOOP (r, read (job_fds[0], &intake, 1));
 123 -  if (r < 0)
 124 -    pfatal_with_name (_("read jobs pipe"));
 125 +      r = pselect (job_fds[0]+1, &readfds, NULL, NULL, specp, &empty);
 126 +      if (r < 0)
 127 +        switch (errno)
 128 +          {
 129 +          case EINTR:
 130 +            /* SIGCHLD will show up as an EINTR.  */
 131 +            return 0;
 132 +
 133 +          case EBADF:
 134 +            /* Someone closed the jobs pipe.
 135 +               That shouldn't happen but if it does we're done.  */
 136 +              O (fatal, NILF, _("job server shut down"));
 137
 138 -  /* What does it mean if read() returns 0?  It shouldn't happen because only
 139 -     the master make can reap all the tokens and close the write side...??  */
 140 -  return r > 0;
 141 +          default:
 142 +            pfatal_with_name (_("pselect jobs pipe"));
 143 +          }
 144 +
 145 +      if (r == 0)
 146 +        /* Timeout.  */
 147 +        return 0;
 148 +
 149 +      /* The read FD is ready: read it!  This is non-blocking.  */
 150 +      EINTRLOOP (r, read (job_fds[0], &intake, 1));
 151 +
 152 +      if (r < 0)
 153 +        {
 154 +          /* Someone sniped our token!  Try again.  */
 155 +          if (errno == EAGAIN)
 156 +            continue;
 157 +
 158 +          pfatal_with_name (_("read jobs pipe"));
 159 +        }
 160 +
 161 +      /* read() should never return 0: only the master make can reap all the
 162 +         tokens and close the write side...??  */
 163 +      return r > 0;
 164 +    }
 165  }
 166
 167  #else
 168 --
 169 cgit v1.0-41-gc330
 170