Linux: Consolidate {RTLD_}SINGLE_THREAD_P definition

Current GLIBC has two ways to implement the single thread optimization
on syscalls to avoid calling the cancellation path: either by using
global variables (__{libc,pthread}_multiple_thread) or by accessing
the TCB field (defined by TLS_MULTIPLE_THREADS_IN_TCB).  Both the
variables and the macros to acces its value are defined in the
architecture sysdep-cancel.h header.

This patch consolidates its definition on only one header,
sysdeps/unix/sysv/linux/sysdep-cancel.h, and adds a new define
(SINGLE_THREAD_BY_GLOBAL) which the architecture defines if it prefer
to use the global variables instead of the TCB field.  This is an
optimization, so if the architecture does not define it, the TCB
method will be used as default.

Checked on x86_64-linux-gnu and on a build with major touched
ABIs (aarch64-linux-gnu, alpha-linux-gnu, arm-linux-gnueabihf,
hppa-linux-gnu, i686-linux-gnu, m68k-linux-gnu, microblaze-linux-gnu,
mips-linux-gnu, mips64-linux-gnu, powerpc-linux-gnu,
powerpc64le-linux-gnu, s390-linux-gnu, s390x-linux-gnu, sh4-linux-gnu,
sparcv9-linux-gnu, sparc64-linux-gnu, tilegx-linux-gnu).

	* sysdeps/unix/sysv/linux/aarch64/sysdep-cancel.h: Remove file.
	* sysdeps/unix/sysv/linux/alpha/sysdep-cancel.h: Likewise.
	* sysdeps/unix/sysv/linux/arm/sysdep-cancel.h: Likewise.
	* sysdeps/unix/sysv/linux/hppa/sysdep-cancel.h: Likewise.
	* sysdeps/unix/sysv/linux/mips/sysdep-cancel.h: Likewise.
	* sysdeps/unix/sysv/linux/nios2/sysdep-cancel.h: Likewise.
	* sysdeps/unix/sysv/linux/powerpc/sysdep-cancel.h: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-32/sysdep-cancel.h: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-64/sysdep-cancel.h: Likewise.
	* sysdeps/unix/sysv/linux/sh/sysdep-cancel.h: Likewise.
	* sysdeps/unix/sysv/linux/sparc/sysdep-cancel.h: Likewise.
	* sysdeps/unix/sysv/linux/tile/sysdep-cancel.h: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/sysdep-cancel.h: Likewise.
	* sysdeps/unix/sysv/linux/s390/s390-64/sysdep.h
	(SINGLE_THREAD_BY_GLOBAL): Define.
	* sysdeps/unix/sysv/linux/aarch64/sysdep.h (SINGLE_THREAD_BY_GLOBAL):
	Likewise.
	* sysdeps/unix/sysv/linux/alpha/sysdep.h (SINGLE_THREAD_BY_GLOBAL):
	Likewise.
	* sysdeps/unix/sysv/linux/arm/sysdep.h (SINGLE_THREAD_BY_GLOBAL):
	Likewise.
	* sysdeps/unix/sysv/linux/hppa/sysdep.h (SINGLE_THREAD_BY_GLOBAL):
	Likewise.
	* sysdeps/unix/sysv/linux/microblaze/sysdep.h
	(SINGLE_THREAD_BY_GLOBAL): Likewise.
	* sysdeps/unix/sysv/linux/x86_64/sysdep.h (SINGLE_THREAD_BY_GLOBAL):
	Likewise.

1 files changed, 64 insertions, 0 deletions

diff --git a/sysdeps/unix/sysv/linux/sysdep-cancel.h b/sysdeps/unix/sysv/linux/sysdep-cancel.h
new file mode 100644
index 0000000000..57bd093de1
--- /dev/null
+++ b/sysdeps/unix/sysv/linux/sysdep-cancel.h
@@ -0,0 +1,64 @@
+/* Single-thread optimization definitions.  Linux version.
+   Copyright (C) 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 <sysdep.h>
+#include <tls.h>
+#include <nptl/pthreadP.h>
+
+/* The default way to check if the process is single thread is by using the
+   pthread_t 'multiple_threads' field.  However for some architectures it
+   is faster to either use an extra field on TCB or global varibles
+   (the TCB field is also used on x86 for some single-thread atomic
+   optimizations).
+
+   The ABI might define SINGLE_THREAD_BY_GLOBAL to enable the single
+   thread check to use global variables instead of the pthread_t
+   field.  */
+
+#ifdef SINGLE_THREAD_BY_GLOBAL
+# if IS_IN (libc)
+extern int __libc_multiple_threads;
+#  define SINGLE_THREAD_P \
+  __glibc_likely (__libc_multiple_threads == 0)
+# elif IS_IN (libpthread)
+extern int __pthread_multiple_threads;
+#  define SINGLE_THREAD_P \
+  __glibc_likely (__pthread_multiple_threads == 0)
+# elif IS_IN (librt)
+#   define SINGLE_THREAD_P					\
+  __glibc_likely (THREAD_GETMEM (THREAD_SELF,			\
+				 header.multiple_threads) == 0)
+# else
+/* For rtld, et cetera.  */
+#  define SINGLE_THREAD_P (1)
+# endif
+#else /* SINGLE_THREAD_BY_GLOBAL  */
+# if IS_IN (libc) || IS_IN (libpthread) || IS_IN (librt)
+#   define SINGLE_THREAD_P					\
+  __glibc_likely (THREAD_GETMEM (THREAD_SELF,			\
+				 header.multiple_threads) == 0)
+# else
+/* For rtld, et cetera.  */
+#  define SINGLE_THREAD_P (1)
+# endif
+#endif /* SINGLE_THREAD_BY_GLOBAL  */
+
+#define RTLD_SINGLE_THREAD_P \
+  __glibc_likely (THREAD_GETMEM (THREAD_SELF, \
+				 header.multiple_threads) == 0)