lib/pthread_sigmask.c

   1 /* POSIX compatible signal blocking for threads.
   2    Copyright (C) 2011-2024 Free Software Foundation, Inc.
   3
   4    This file is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU Lesser General Public License as
   6    published by the Free Software Foundation; either version 2.1 of the
   7    License, or (at your option) any later version.
   8
   9    This file is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 #include <config.h>
  18
  19 /* Specification.  */
  20 #include <signal.h>
  21
  22 #include <errno.h>
  23 #include <stddef.h>
  24
  25 #if PTHREAD_SIGMASK_INEFFECTIVE
  26 # include <string.h>
  27 #endif
  28
  29 #if PTHREAD_SIGMASK_UNBLOCK_BUG
  30 # include <unistd.h>
  31 #endif
  32
  33 int
  34 pthread_sigmask (int how, const sigset_t *new_mask, sigset_t *old_mask)
  35 #undef pthread_sigmask
  36 {
  37 #if HAVE_PTHREAD_SIGMASK
  38   int ret;
  39
  40 # if PTHREAD_SIGMASK_INEFFECTIVE
  41   sigset_t omask, omask_copy;
  42   sigset_t *old_mask_ptr = &omask;
  43   sigemptyset (&omask);
  44   /* Add a signal unlikely to be blocked, so that OMASK_COPY
  45      is unlikely to match the actual mask.  */
  46   sigaddset (&omask, SIGILL);
  47   memcpy (&omask_copy, &omask, sizeof omask);
  48 # else
  49   sigset_t *old_mask_ptr = old_mask;
  50 # endif
  51
  52   ret = pthread_sigmask (how, new_mask, old_mask_ptr);
  53
  54 # if PTHREAD_SIGMASK_INEFFECTIVE
  55   if (ret == 0)
  56     {
  57       /* Detect whether pthread_sigmask is currently ineffective.
  58          Don't cache the information: libpthread.so could be dynamically
  59          loaded after the program started and after pthread_sigmask was
  60          called for the first time.  */
  61       if (memcmp (&omask_copy, &omask, sizeof omask) == 0
  62           && pthread_sigmask (1729, &omask_copy, NULL) == 0)
  63         {
  64           /* pthread_sigmask is currently ineffective.  The program is not
  65              linked to -lpthread.  So use sigprocmask instead.  */
  66           return (sigprocmask (how, new_mask, old_mask) < 0 ? errno : 0);
  67         }
  68
  69       if (old_mask)
  70         memcpy (old_mask, &omask, sizeof omask);
  71     }
  72 # endif
  73 # if PTHREAD_SIGMASK_FAILS_WITH_ERRNO
  74   if (ret == -1)
  75     return errno;
  76 # endif
  77 # if PTHREAD_SIGMASK_UNBLOCK_BUG
  78   if (ret == 0
  79       && new_mask != NULL
  80       && (how == SIG_UNBLOCK || how == SIG_SETMASK))
  81     {
  82       /* Give the OS the opportunity to raise signals that were pending before
  83          the pthread_sigmask call and have now been unblocked.  */
  84       usleep (1);
  85     }
  86 # endif
  87   return ret;
  88 #else
  89   int ret = sigprocmask (how, new_mask, old_mask);
  90   return (ret < 0 ? errno : 0);
  91 #endif
  92 }