Replace __libc_multiple_threads with __libc_single_threaded

And also fixes the SINGLE_THREAD_P macro for SINGLE_THREAD_BY_GLOBAL,
since header inclusion single-thread.h is in the wrong order, the define
needs to come before including sysdeps/unix/sysdep.h.  The macro
is now moved to a per-arch single-threade.h header.

The SINGLE_THREAD_P is used on some more places.

Checked on aarch64-linux-gnu and x86_64-linux-gnu.

nptl/Makefile

@@ -50,7 +50,6 @@ routines = \
   events \
   futex-internal \
   libc-cleanup \
-  libc_multiple_threads \
   lowlevellock \
   nptl-stack \
   nptl_deallocate_tsd \

nptl/allocatestack.c

@@ -292,9 +292,6 @@ allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
 
       /* This is at least the second thread.  */
       pd->header.multiple_threads = 1;
-#ifndef TLS_MULTIPLE_THREADS_IN_TCB
-      __libc_multiple_threads = 1;
-#endif
 
 #ifdef NEED_DL_SYSINFO
       SETUP_THREAD_SYSINFO (pd);
@@ -413,9 +410,6 @@ allocate_stack (const struct pthread_attr *attr, struct pthread **pdp,
 
 	  /* This is at least the second thread.  */
 	  pd->header.multiple_threads = 1;
-#ifndef TLS_MULTIPLE_THREADS_IN_TCB
-	  __libc_multiple_threads = 1;
-#endif
 
 #ifdef NEED_DL_SYSINFO
 	  SETUP_THREAD_SYSINFO (pd);

nptl/libc_multiple_threads.c

@@ -1,28 +0,0 @@
-/* Copyright (C) 2002-2022 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
-   <https://www.gnu.org/licenses/>.  */
-
-#include <pthreadP.h>
-
-#if IS_IN (libc)
-# ifndef TLS_MULTIPLE_THREADS_IN_TCB
-/* Variable set to a nonzero value either if more than one thread runs or ran,
-   or if a single-threaded process is trying to cancel itself.  See
-   nptl/descr.h for more context on the single-threaded process case.  */
-int __libc_multiple_threads;
-libc_hidden_data_def (__libc_multiple_threads)
-# endif
-#endif

nptl/pthread_cancel.c

@@ -161,7 +161,7 @@ __pthread_cancel (pthread_t th)
 	   points get executed.  */
 	THREAD_SETMEM (THREAD_SELF, header.multiple_threads, 1);
 #ifndef TLS_MULTIPLE_THREADS_IN_TCB
-      __libc_multiple_threads = 1;
+	__libc_single_threaded_internal = 0;
 #endif
     }
   while (!atomic_compare_exchange_weak_acquire (&pd->cancelhandling, &oldval,

posix/fork.c

@@ -45,7 +45,7 @@ __libc_fork (void)
      requirement for fork (Austin Group tracker issue #62) this is
      best effort to make is async-signal-safe at least for single-thread
      case.  */
-  bool multiple_threads = __libc_single_threaded_internal == 0;
+  bool multiple_threads = !SINGLE_THREAD_P;
   uint64_t lastrun;
 
   lastrun = __run_prefork_handlers (multiple_threads);

sysdeps/nptl/setxid.h

@@ -29,7 +29,7 @@
 #define INLINE_SETXID_SYSCALL(name, nr, args...) \
   ({									\
     int __result;							\
-    if (!__libc_single_threaded_internal)				\
+    if (!SINGLE_THREAD_P)						\
       {									\
 	struct xid_command __cmd;					\
 	__cmd.syscall_no = __NR_##name;					\

sysdeps/unix/sysv/linux/aarch64/single-thread.h

@@ -0,0 +1,2 @@
+#define SINGLE_THREAD_BY_GLOBAL
+#include_next <single-thread.h>

sysdeps/unix/sysv/linux/aarch64/sysdep.h

@@ -164,8 +164,6 @@
 # define HAVE_CLOCK_GETTIME64_VSYSCALL	"__kernel_clock_gettime"
 # define HAVE_GETTIMEOFDAY_VSYSCALL	"__kernel_gettimeofday"
 
-# define SINGLE_THREAD_BY_GLOBAL		1
-
 # undef INTERNAL_SYSCALL_RAW
 # define INTERNAL_SYSCALL_RAW(name, nr, args...)		\
   ({ long _sys_result;						\

sysdeps/unix/sysv/linux/alpha/sysdep.h

@@ -32,8 +32,6 @@
 #undef SYS_ify
 #define SYS_ify(syscall_name)	__NR_##syscall_name
 
-#define SINGLE_THREAD_BY_GLOBAL 1
-
 #ifdef __ASSEMBLER__
 #include <asm/pal.h>
 #include <alpha/regdef.h>

sysdeps/unix/sysv/linux/arc/single-thread.h

@@ -0,0 +1,2 @@
+#define SINGLE_THREAD_BY_GLOBAL
+#include_next <single-thread.h>

sysdeps/unix/sysv/linux/arc/sysdep.h

@@ -132,8 +132,6 @@ L (call_syscall_err):			ASM_LINE_SEP	\
 
 #else  /* !__ASSEMBLER__ */
 
-# define SINGLE_THREAD_BY_GLOBAL		1
-
 # if IS_IN (libc)
 extern long int __syscall_error (long int);
 hidden_proto (__syscall_error)

sysdeps/unix/sysv/linux/arm/single-thread.h

@@ -0,0 +1,2 @@
+#define SINGLE_THREAD_BY_GLOBAL
+#include_next <single-thread.h>

sysdeps/unix/sysv/linux/arm/sysdep.h

@@ -408,8 +408,6 @@ __local_syscall_error:						\
 #define INTERNAL_SYSCALL_NCS(number, nr, args...)              \
   INTERNAL_SYSCALL_RAW (number, nr, args)
 
-#define SINGLE_THREAD_BY_GLOBAL	1
-
 #endif	/* __ASSEMBLER__ */
 
 #endif /* linux/arm/sysdep.h */

sysdeps/unix/sysv/linux/hppa/single-thread.h

@@ -0,0 +1,2 @@
+#define SINGLE_THREAD_BY_GLOBAL
+#include_next <single-thread.h>

sysdeps/unix/sysv/linux/hppa/sysdep.h

@@ -474,6 +474,4 @@ L(pre_end):					ASM_LINE_SEP	\
 #define PTR_MANGLE(var) (void) (var)
 #define PTR_DEMANGLE(var) (void) (var)
 
-#define SINGLE_THREAD_BY_GLOBAL	1
-
 #endif /* _LINUX_HPPA_SYSDEP_H */

sysdeps/unix/sysv/linux/microblaze/single-thread.h

@@ -0,0 +1,2 @@
+#define SINGLE_THREAD_BY_GLOBAL
+#include_next <single-thread.h>

sysdeps/unix/sysv/linux/microblaze/sysdep.h

@@ -308,8 +308,6 @@ SYSCALL_ERROR_LABEL_DCL:                            \
 # define PTR_MANGLE(var) (void) (var)
 # define PTR_DEMANGLE(var) (void) (var)
 
-# define SINGLE_THREAD_BY_GLOBAL	1
-
 #undef HAVE_INTERNAL_BRK_ADDR_SYMBOL
 #define HAVE_INTERNAL_BRK_ADDR_SYMBOL 1
 

sysdeps/unix/sysv/linux/s390/single-thread.h

@@ -0,0 +1,2 @@
+#define SINGLE_THREAD_BY_GLOBAL
+#include_next <single-thread.h>

sysdeps/unix/sysv/linux/s390/sysdep.h

@@ -93,9 +93,6 @@
 #define ASMFMT_5 , "0" (gpr2), "d" (gpr3), "d" (gpr4), "d" (gpr5), "d" (gpr6)
 #define ASMFMT_6 , "0" (gpr2), "d" (gpr3), "d" (gpr4), "d" (gpr5), "d" (gpr6), "d" (gpr7)
 
-#define SINGLE_THREAD_BY_GLOBAL		1
-
-
 #define VDSO_NAME  "LINUX_2.6.29"
 #define VDSO_HASH  123718585
 

sysdeps/unix/sysv/linux/single-thread.h

@@ -19,6 +19,10 @@
 #ifndef _SINGLE_THREAD_H
 #define _SINGLE_THREAD_H
 
+#ifndef __ASSEMBLER__
+# include <sys/single_threaded.h>
+#endif
+
 /* 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 variables (the TCB
@@ -27,16 +31,11 @@
    The ABI might define SINGLE_THREAD_BY_GLOBAL to enable the single thread
    check to use global variables instead of the pthread_t field.  */
 
-#ifndef __ASSEMBLER__
-extern int __libc_multiple_threads;
-libc_hidden_proto (__libc_multiple_threads)
-#endif
-
 #if !defined SINGLE_THREAD_BY_GLOBAL || IS_IN (rtld)
 # define SINGLE_THREAD_P \
   (THREAD_GETMEM (THREAD_SELF, header.multiple_threads) == 0)
 #else
-# define SINGLE_THREAD_P (__libc_multiple_threads == 0)
+# define SINGLE_THREAD_P (__libc_single_threaded_internal != 0)
 #endif
 
 #define RTLD_SINGLE_THREAD_P SINGLE_THREAD_P

sysdeps/unix/sysv/linux/x86_64/single-thread.h

@@ -0,0 +1,2 @@
+#define SINGLE_THREAD_BY_GLOBAL
+#include_next <single-thread.h>

sysdeps/unix/sysv/linux/x86_64/sysdep.h

@@ -379,8 +379,6 @@
 
 # define HAVE_CLONE3_WRAPPER			1
 
-# define SINGLE_THREAD_BY_GLOBAL		1
-
 #endif	/* __ASSEMBLER__ */