diff --git a/manual/signal.texi b/manual/signal.texi
index 9577ff0..4f0ef59 100644
--- a/manual/signal.texi
+++ b/manual/signal.texi
@@ -235,6 +235,7 @@ defined.  Since the signal numbers are allocated consecutively,
 * Job Control Signals::         Signals used to support job control.
 * Operation Error Signals::     Used to report operational system errors.
 * Miscellaneous Signals::       Miscellaneous Signals.
+* Internally-Used Signals::     Signals used internally by the C library.
 * Signal Messages::             Printing a message describing a signal.
 @end menu
 
@@ -794,6 +795,26 @@ in @ref{Signaling Another Process}.
 The default action is to terminate the process.
 @end deftypevr
 
+@deftypevr Macro int SIGRTMIN
+@deftypevrx Macro int SIGRTMAX
+@standards{POSIX.1, signal.h}
+@cindex real-time signals
+The range of signal numbers @code{SIGRTMIN}, @code{SIGRTMIN+1},
+@dots{}, @code{SIGRTMAX} is also set aside for you to use any way you
+want.  In addition, these signals (and no others) are guaranteed to
+support @dfn{real-time} signal semantics, which unfortunately this
+manual does not yet document.
+
+Unlike all of the other signal number macros, @code{SIGRTMIN} and
+@code{SIGRTMAX} are not compile-time constants, because some operating
+systems make the number of real-time signals tunable on a
+per-installation or even per-process basis.  However, POSIX guarantees
+that there will be at least 8 signal numbers in this range.
+
+The default action for all signals in this range is to terminate the
+process.
+@end deftypevr
+
 @deftypevr Macro int SIGWINCH
 @standards{BSD, signal.h}
 Window size change.  This is generated on some systems (including GNU)
@@ -817,6 +838,22 @@ to print some status information about the system and what the process
 is doing.  Otherwise the default is to do nothing.
 @end deftypevr
 
+@node Internally-Used Signals
+@subsection Internally-Used Signals
+@cindex internally used signals
+
+On some operating systems, @theglibc{} needs to use a few signals from
+the ``true'' real-time range internally, to implement thread
+cancellation, cross-thread effective ID synchronization, POSIX timer
+management, etc.  @Theglibc{} adjusts @code{SIGRTMIN} and
+@code{SIGRTMAX} to exclude these signals, and it also takes steps to
+prevent application code from altering their state: @code{sigprocmask}
+cannot block them and @code{sigaction} cannot redefine their handlers,
+for instance.  Therefore, most programs do not need to know or care
+about these signals.  We mainly document their existence for the sake
+of anyone who has ever wondered why there is a gap between the
+highest-numbered ``normal'' signal and @code{SIGRTMIN} on Linux.
+
 @node Signal Messages
 @subsection Signal Messages
 @cindex signal messages
diff --git a/sysdeps/unix/sysv/linux/alpha/sigprocmask.c b/sysdeps/unix/sysv/linux/alpha/sigprocmask.c
deleted file mode 100644
index ebec70c..0000000
--- a/sysdeps/unix/sysv/linux/alpha/sigprocmask.c
+++ /dev/null
@@ -1,58 +0,0 @@
-/* Copyright (C) 1993-2017 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-   Contributed by David Mosberger (davidm@azstarnet.com).
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library.  If not, see
-   <http://www.gnu.org/licenses/>.  */
-
-#include <errno.h>
-#include <sysdep.h>
-#include <signal.h>
-
-/* When there is kernel support for more than 64 signals, we'll have to
-   switch to a new system call convention here.  */
-
-int
-__sigprocmask (int how, const sigset_t *set, sigset_t *oset)
-{
-  unsigned long int setval;
-  long result;
-
-  if (set)
-    setval = set->__val[0];
-  else
-    {
-      setval = 0;
-      how = SIG_BLOCK;	/* ensure blocked mask doesn't get changed */
-    }
-
-  result = INLINE_SYSCALL (osf_sigprocmask, 2, how, setval);
-  if (result == -1)
-    /* If there are ever more than 63 signals, we need to recode this
-       in assembler since we wouldn't be able to distinguish a mask of
-       all 1s from -1, but for now, we're doing just fine... */
-    return result;
-
-  if (oset)
-    {
-      oset->__val[0] = result;
-      result = _SIGSET_NWORDS;
-      while (--result > 0)
-	oset->__val[result] = 0;
-    }
-  return 0;
-}
-
-libc_hidden_def (__sigprocmask)
-weak_alias (__sigprocmask, sigprocmask);
diff --git a/sysdeps/unix/sysv/linux/ia64/sigprocmask.c b/sysdeps/unix/sysv/linux/ia64/sigprocmask.c
deleted file mode 100644
index 920c5fd..0000000
--- a/sysdeps/unix/sysv/linux/ia64/sigprocmask.c
+++ /dev/null
@@ -1,40 +0,0 @@
-/* Copyright (C) 1997-2017 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-   Linux/IA64 specific sigprocmask
-   Written by Jes Sorensen, <Jes.Sorensen@cern.ch>, April 1999.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <http://www.gnu.org/licenses/>.  */
-
-/* Linux/ia64 only has rt signals, thus we do not even want to try falling
-   back to the old style signals as the default Linux handler does. */
-
-#include <errno.h>
-#include <signal.h>
-#include <unistd.h>
-
-#include <sysdep.h>
-#include <sys/syscall.h>
-
-/* Get and/or change the set of blocked signals.  */
-int
-__sigprocmask (int how, const sigset_t *set, sigset_t *oset)
-{
-
-  /* XXX The size argument hopefully will have to be changed to the
-     real size of the user-level sigset_t.  */
-  return INLINE_SYSCALL (rt_sigprocmask, 4, how, set, oset, _NSIG / 8);
-}
-libc_hidden_def (__sigprocmask)
-weak_alias (__sigprocmask, sigprocmask)
diff --git a/sysdeps/unix/sysv/linux/internal-signals.h b/sysdeps/unix/sysv/linux/internal-signals.h
index e96a718..bb8234d 100644
--- a/sysdeps/unix/sysv/linux/internal-signals.h
+++ b/sysdeps/unix/sysv/linux/internal-signals.h
@@ -36,6 +36,12 @@
 #define SIGSETXID       (__SIGRTMIN + 1)
 
 
+static inline bool
+__has_internal_signal (const sigset_t *set)
+{
+  return __sigismember (set, SIGCANCEL) || __sigismember (set, SIGSETXID);
+}
+
 /* Return is sig is used internally.  */
 static inline int
 __is_internal_signal (int sig)
diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/sigprocmask.c b/sysdeps/unix/sysv/linux/s390/s390-64/sigprocmask.c
deleted file mode 100644
index a8010e7..0000000
--- a/sysdeps/unix/sysv/linux/s390/s390-64/sigprocmask.c
+++ /dev/null
@@ -1,38 +0,0 @@
-/* Copyright (C) 2001-2017 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <http://www.gnu.org/licenses/>.  */
-
-/* 64 bit Linux for S/390 only has rt signals, thus we do not even want to try
-   falling back to the old style signals as the default Linux handler does. */
-
-#include <errno.h>
-#include <signal.h>
-#include <unistd.h>
-
-#include <sysdep.h>
-#include <sys/syscall.h>
-
-/* Get and/or change the set of blocked signals.  */
-int
-__sigprocmask (int how, const sigset_t *set, sigset_t *oset)
-{
-
-  /* XXX The size argument hopefully will have to be changed to the
-     real size of the user-level sigset_t.  */
-  return INLINE_SYSCALL (rt_sigprocmask, 4, how, set, oset, _NSIG / 8);
-}
-libc_hidden_def (__sigprocmask)
-weak_alias (__sigprocmask, sigprocmask)
diff --git a/sysdeps/unix/sysv/linux/sigprocmask.c b/sysdeps/unix/sysv/linux/sigprocmask.c
index e776563..e574b5d 100644
--- a/sysdeps/unix/sysv/linux/sigprocmask.c
+++ b/sysdeps/unix/sysv/linux/sigprocmask.c
@@ -1,4 +1,5 @@
-/* Copyright (C) 1997-2017 Free Software Foundation, Inc.
+/* Get and/or change the set of blocked signals.  Linux version.
+   Copyright (C) 1997-2017 Free Software Foundation, Inc.
    This file is part of the GNU C Library.
 
    The GNU C Library is free software; you can redistribute it and/or
@@ -17,34 +18,22 @@
 
 #include <errno.h>
 #include <signal.h>
-#include <string.h>  /* Needed for string function builtin redirection.  */
-#include <unistd.h>
+#include <internal-signals.h>
 
-#include <sysdep.h>
-#include <sys/syscall.h>
 
-#include <nptl/pthreadP.h>              /* SIGCANCEL, SIGSETXID */
-
-
-/* Get and/or change the set of blocked signals.  */
 int
 __sigprocmask (int how, const sigset_t *set, sigset_t *oset)
 {
   sigset_t local_newmask;
 
-  /* The only thing we have to make sure here is that SIGCANCEL and
-     SIGSETXID are not blocked.  */
-  if (set != NULL
-      && (__builtin_expect (__sigismember (set, SIGCANCEL), 0)
-	  || __builtin_expect (__sigismember (set, SIGSETXID), 0)))
+  if (set != NULL && __glibc_unlikely (__has_internal_signal (set)))
     {
       local_newmask = *set;
-      __sigdelset (&local_newmask, SIGCANCEL);
-      __sigdelset (&local_newmask, SIGSETXID);
+      __clear_internal_signals (&local_newmask);
       set = &local_newmask;
     }
 
-  return INLINE_SYSCALL (rt_sigprocmask, 4, how, set, oset, _NSIG / 8);
+  return INLINE_SYSCALL_CALL (rt_sigprocmask, how, set, oset, _NSIG / 8);
 }
 libc_hidden_def (__sigprocmask)
 weak_alias (__sigprocmask, sigprocmask)
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/sigprocmask.c b/sysdeps/unix/sysv/linux/sparc/sparc64/sigprocmask.c
deleted file mode 100644
index ef7d7fe..0000000
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/sigprocmask.c
+++ /dev/null
@@ -1,34 +0,0 @@
-/* Copyright (C) 1997-2017 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <http://www.gnu.org/licenses/>.  */
-
-#include <errno.h>
-#include <signal.h>
-#include <unistd.h>
-
-#include <sysdep.h>
-#include <sys/syscall.h>
-
-/* Get and/or change the set of blocked signals.  */
-int
-__sigprocmask (int how, const sigset_t *set, sigset_t *oset)
-{
-  /* XXX The size argument hopefully will have to be changed to the
-     real size of the user-level sigset_t.  */
-  return INLINE_SYSCALL (rt_sigprocmask, 4, how, set, oset, _NSIG / 8);
-}
-libc_hidden_def (__sigprocmask)
-weak_alias (__sigprocmask, sigprocmask)
diff --git a/sysdeps/unix/sysv/linux/x86_64/sigprocmask.c b/sysdeps/unix/sysv/linux/x86_64/sigprocmask.c
deleted file mode 100644
index 1610ddf..0000000
--- a/sysdeps/unix/sysv/linux/x86_64/sigprocmask.c
+++ /dev/null
@@ -1,39 +0,0 @@
-/* Copyright (C) 1997-2017 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-   Written by Jes Sorensen, <Jes.Sorensen@cern.ch>, April 1999.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <http://www.gnu.org/licenses/>.  */
-
-/* Linux/x86_64 only has rt signals, thus we do not even want to try falling
-   back to the old style signals as the default Linux handler does. */
-
-#include <errno.h>
-#include <signal.h>
-#include <unistd.h>
-
-#include <sysdep.h>
-#include <sys/syscall.h>
-
-/* Get and/or change the set of blocked signals.  */
-int
-__sigprocmask (int how, const sigset_t *set, sigset_t *oset)
-{
-
-  /* XXX The size argument hopefully will have to be changed to the
-     real size of the user-level sigset_t.  */
-  return INLINE_SYSCALL (rt_sigprocmask, 4, how, set, oset, _NSIG / 8);
-}
-libc_hidden_def (__sigprocmask)
-weak_alias (__sigprocmask, sigprocmask)
