nptl: Remove ATOMIC_EXCHANGE_USES_CAS usageazanella/atomic-cleanup

The only usage was for pthread_spin_lock, introduced by 12d2dd706099aa4,
as a way to optimize the code for certain architectures. Now that atomic
builtins are used by default, let the compiler use the best code sequence
for the atomic exchange.

Co-authored-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

20 files changed, 33 insertions, 354 deletions

diff --git a/sysdeps/aarch64/atomic-machine.h b/sysdeps/aarch64/atomic-machine.h
deleted file mode 100644
index 002a800358..0000000000
--- a/sysdeps/aarch64/atomic-machine.h
+++ /dev/null
@@ -1,24 +0,0 @@
-/* Copyright (C) 2003-2025 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/>.  */
-
-#ifndef _AARCH64_ATOMIC_MACHINE_H
-#define _AARCH64_ATOMIC_MACHINE_H	1
-
-#define ATOMIC_EXCHANGE_USES_CAS 0
-
-#endif
diff --git a/sysdeps/alpha/atomic-machine.h b/sysdeps/alpha/atomic-machine.h
index 9844f13079..9aec231748 100644
--- a/sysdeps/alpha/atomic-machine.h
+++ b/sysdeps/alpha/atomic-machine.h
@@ -17,7 +17,4 @@
 
 #include <stdint.h>
 
-/* XXX Is this actually correct?  */
-#define ATOMIC_EXCHANGE_USES_CAS 1
-
 #define atomic_write_barrier()	__asm ("wmb" : : : "memory");
diff --git a/sysdeps/arc/atomic-machine.h b/sysdeps/arc/atomic-machine.h
deleted file mode 100644
index 69b9328fc8..0000000000
--- a/sysdeps/arc/atomic-machine.h
+++ /dev/null
@@ -1,26 +0,0 @@
-/* Low-level functions for atomic operations. ARC version.
-   Copyright (C) 2020-2025 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/>.  */
-
-#ifndef _ARC_BITS_ATOMIC_H
-#define _ARC_BITS_ATOMIC_H 1
-
-/* ARC does have legacy atomic EX reg, [mem] instruction but the micro-arch
-   is not as optimal as LLOCK/SCOND specially for SMP.  */
-#define ATOMIC_EXCHANGE_USES_CAS 1
-
-#endif /* _ARC_BITS_ATOMIC_H */
diff --git a/sysdeps/arm/atomic-machine.h b/sysdeps/arm/atomic-machine.h
deleted file mode 100644
index 7aee873371..0000000000
--- a/sysdeps/arm/atomic-machine.h
+++ /dev/null
@@ -1,19 +0,0 @@
-/* Atomic operations.  Pure ARM version.
-   Copyright (C) 2002-2025 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/>.  */
-
-#define ATOMIC_EXCHANGE_USES_CAS 1
diff --git a/sysdeps/csky/atomic-machine.h b/sysdeps/csky/atomic-machine.h
deleted file mode 100644
index 84468cd66e..0000000000
--- a/sysdeps/csky/atomic-machine.h
+++ /dev/null
@@ -1,24 +0,0 @@
-/* Atomic operations.  C-SKY version.
-   Copyright (C) 2018-2025 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/>.  */
-
-#ifndef __CSKY_ATOMIC_H_
-#define __CSKY_ATOMIC_H_
-
-#define ATOMIC_EXCHANGE_USES_CAS 1
-
-#endif /* atomic-machine.h */
diff --git a/sysdeps/generic/atomic-machine.h b/sysdeps/generic/atomic-machine.h
index 3ef5eb60d7..9f8528c1f2 100644
--- a/sysdeps/generic/atomic-machine.h
+++ b/sysdeps/generic/atomic-machine.h
@@ -18,24 +18,20 @@
 #ifndef _ATOMIC_MACHINE_H
 #define _ATOMIC_MACHINE_H	1
 
-/* We have by default no support for atomic operations.  So define
-   them non-atomic.  If this is a problem somebody will have to come
-   up with real definitions.  */
-
-/* The only basic operation needed is compare and exchange.  */
-#define atomic_compare_and_exchange_val_acq(mem, newval, oldval) \
-  ({ __typeof (mem) __gmemp = (mem);				      \
-     __typeof (*mem) __gret = *__gmemp;				      \
-     __typeof (*mem) __gnewval = (newval);			      \
-								      \
-     if (__gret == (oldval))					      \
-       *__gmemp = __gnewval;					      \
-     __gret; })
-
-#define atomic_compare_and_exchange_bool_acq(mem, newval, oldval) \
-  ({ __typeof (mem) __gmemp = (mem);				      \
-     __typeof (*mem) __gnewval = (newval);			      \
-								      \
-     *__gmemp == (oldval) ? (*__gmemp = __gnewval, 0) : 1; })
+/* Some macros can be overridden if the architecture requires some specific
+   atomic operations or provides extra optimizations.
+
+   * atomic_max (mem, value): atomically set the maximum value of *mem
+     and value to *mem.  Used on malloc statistics collection.
+
+   * atomic_full_barrier: defaults to __atomic_thread_fence (__ATOMIC_SEQ_CST)
+
+   * atomic_read_barrier: defaults to __atomic_thread_fence (__ATOMIC_ACQUIRE)
+
+   * atomic_write_barrier: defaults to __atomic_thread_fence (__ATOMIC_RELEASE)
+
+   * atomic_spin_nop: arch-specific instruction used on pthread spin lock
+     and adaptive mutexes to optimize spin-wait loops.
+*/
 
 #endif	/* atomic-machine.h */
diff --git a/sysdeps/hppa/atomic-machine.h b/sysdeps/hppa/atomic-machine.h
deleted file mode 100644
index 92d386b748..0000000000
--- a/sysdeps/hppa/atomic-machine.h
+++ /dev/null
@@ -1,24 +0,0 @@
-/* Copyright (C) 2003-2025 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/>.  */
-
-#ifndef _ATOMIC_MACHINE_H
-#define _ATOMIC_MACHINE_H	1
-
-/* XXX Is this actually correct?  */
-#define ATOMIC_EXCHANGE_USES_CAS 1
-
-#endif
diff --git a/sysdeps/loongarch/atomic-machine.h b/sysdeps/loongarch/atomic-machine.h
deleted file mode 100644
index 20cc170735..0000000000
--- a/sysdeps/loongarch/atomic-machine.h
+++ /dev/null
@@ -1,24 +0,0 @@
-/* Atomic operations.
-   Copyright (C) 2022-2025 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/>.  */
-
-#ifndef _LINUX_LOONGARCH_BITS_ATOMIC_H
-#define _LINUX_LOONGARCH_BITS_ATOMIC_H 1
-
-#define ATOMIC_EXCHANGE_USES_CAS 0
-
-#endif /* bits/atomic.h */
diff --git a/sysdeps/m68k/atomic-machine.h b/sysdeps/m68k/atomic-machine.h
deleted file mode 100644
index 8542affba0..0000000000
--- a/sysdeps/m68k/atomic-machine.h
+++ /dev/null
@@ -1,28 +0,0 @@
-/* Copyright (C) 2003-2025 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/>.  */
-
-#ifndef _M68K_ATOMIC_MACHINE_H
-#define _M68K_ATOMIC_MACHINE_H	1
-
-#if defined __mc68020__ || defined __mcoldfire__
-/* XXX Is this actually correct?  */
-# define ATOMIC_EXCHANGE_USES_CAS 1
-#else
-# error "ISAs does not support atomic operations"
-#endif
-
-#endif
diff --git a/sysdeps/microblaze/atomic-machine.h b/sysdeps/microblaze/atomic-machine.h
deleted file mode 100644
index 8c04235b69..0000000000
--- a/sysdeps/microblaze/atomic-machine.h
+++ /dev/null
@@ -1,22 +0,0 @@
-/* Copyright (C) 2003-2025 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 <sysdep.h>
-
-/* XXX Is this actually correct?  */
-#define ATOMIC_EXCHANGE_USES_CAS 1
diff --git a/sysdeps/mips/atomic-machine.h b/sysdeps/mips/atomic-machine.h
deleted file mode 100644
index 9294fb76d9..0000000000
--- a/sysdeps/mips/atomic-machine.h
+++ /dev/null
@@ -1,38 +0,0 @@
-/* Low-level functions for atomic operations. Mips version.
-   Copyright (C) 2005-2025 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/>.  */
-
-#ifndef _MIPS_ATOMIC_MACHINE_H
-#define _MIPS_ATOMIC_MACHINE_H 1
-
-#include <sgidefs.h>
-
-#if _MIPS_SIM == _ABIO32 && __mips < 2
-#define MIPS_PUSH_MIPS2 ".set	mips2\n\t"
-#else
-#define MIPS_PUSH_MIPS2
-#endif
-
-/* MIPS is an LL/SC machine.  However, XLP has a direct atomic exchange
-   instruction which will be used by __atomic_exchange_n.  */
-#ifdef _MIPS_ARCH_XLP
-# define ATOMIC_EXCHANGE_USES_CAS 0
-#else
-# define ATOMIC_EXCHANGE_USES_CAS 1
-#endif
-
-#endif /* atomic-machine.h */
diff --git a/sysdeps/or1k/atomic-machine.h b/sysdeps/or1k/atomic-machine.h
deleted file mode 100644
index 51bc8a0ff4..0000000000
--- a/sysdeps/or1k/atomic-machine.h
+++ /dev/null
@@ -1,24 +0,0 @@
-/* Atomic operations.  OpenRISC version.
-   Copyright (C) 2022-2025 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/>.  */
-
-#ifndef __OR1K_ATOMIC_H_
-#define __OR1K_ATOMIC_H_
-
-#define ATOMIC_EXCHANGE_USES_CAS 1
-
-#endif /* atomic-machine.h */
diff --git a/sysdeps/powerpc/atomic-machine.h b/sysdeps/powerpc/atomic-machine.h
deleted file mode 100644
index 988cc4f435..0000000000
--- a/sysdeps/powerpc/atomic-machine.h
+++ /dev/null
@@ -1,34 +0,0 @@
-/* Atomic operations.  PowerPC Common version.
-   Copyright (C) 2003-2025 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/>.  */
-
-#ifndef _POWERPC_ATOMIC_MACHINE_H
-#define _POWERPC_ATOMIC_MACHINE_H       1
-
-#define ATOMIC_EXCHANGE_USES_CAS 1
-
-/* Used on pthread_spin_{try}lock.  */
-#define __ARCH_ACQ_INSTR        "isync"
-#if defined _ARCH_PWR6 || defined _ARCH_PWR6X
-# define MUTEX_HINT_ACQ	",1"
-# define MUTEX_HINT_REL	",0"
-#else
-# define MUTEX_HINT_ACQ
-# define MUTEX_HINT_REL
-#endif
-
-#endif
diff --git a/sysdeps/powerpc/nptl/pthread_spin_lock.c b/sysdeps/powerpc/nptl/pthread_spin_lock.c
index b4be60f533..4317c03336 100644
--- a/sysdeps/powerpc/nptl/pthread_spin_lock.c
+++ b/sysdeps/powerpc/nptl/pthread_spin_lock.c
@@ -18,6 +18,15 @@
 #include "pthreadP.h"
 #include <shlib-compat.h>
 
+#define __ARCH_ACQ_INSTR        "isync"
+#if defined _ARCH_PWR6 || defined _ARCH_PWR6X
+# define MUTEX_HINT_ACQ	",1"
+# define MUTEX_HINT_REL	",0"
+#else
+# define MUTEX_HINT_ACQ
+# define MUTEX_HINT_REL
+#endif
+
 int
 __pthread_spin_lock (pthread_spinlock_t *lock)
 {
diff --git a/sysdeps/powerpc/nptl/pthread_spin_trylock.c b/sysdeps/powerpc/nptl/pthread_spin_trylock.c
index 457e61397c..fd5f89ed98 100644
--- a/sysdeps/powerpc/nptl/pthread_spin_trylock.c
+++ b/sysdeps/powerpc/nptl/pthread_spin_trylock.c
@@ -19,6 +19,15 @@
 #include "pthreadP.h"
 #include <shlib-compat.h>
 
+#define __ARCH_ACQ_INSTR        "isync"
+#if defined _ARCH_PWR6 || defined _ARCH_PWR6X
+# define MUTEX_HINT_ACQ	",1"
+# define MUTEX_HINT_REL	",0"
+#else
+# define MUTEX_HINT_ACQ
+# define MUTEX_HINT_REL
+#endif
+
 int
 __pthread_spin_trylock (pthread_spinlock_t *lock)
 {
diff --git a/sysdeps/riscv/atomic-machine.h b/sysdeps/riscv/atomic-machine.h
index 5d2ad331cc..b6494b3c83 100644
--- a/sysdeps/riscv/atomic-machine.h
+++ b/sysdeps/riscv/atomic-machine.h
@@ -21,8 +21,6 @@
 
 #ifdef __riscv_atomic
 
-# define ATOMIC_EXCHANGE_USES_CAS 0
-
 /* Miscellaneous.  */
 
 # define asm_amo(which, ordering, mem, value) ({ 		\
diff --git a/sysdeps/s390/atomic-machine.h b/sysdeps/s390/atomic-machine.h
deleted file mode 100644
index b1646d1b07..0000000000
--- a/sysdeps/s390/atomic-machine.h
+++ /dev/null
@@ -1,18 +0,0 @@
-/* Copyright (C) 2003-2025 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/>.  */
-
-#define ATOMIC_EXCHANGE_USES_CAS 1
diff --git a/sysdeps/sh/atomic-machine.h b/sysdeps/sh/atomic-machine.h
deleted file mode 100644
index b012d6f056..0000000000
--- a/sysdeps/sh/atomic-machine.h
+++ /dev/null
@@ -1,20 +0,0 @@
-/* Atomic operations used inside libc.  Linux/SH version.
-   Copyright (C) 2003-2025 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/>.  */
-
-/* XXX Is this actually correct?  */
-#define ATOMIC_EXCHANGE_USES_CAS 1
diff --git a/sysdeps/sparc/atomic-machine.h b/sysdeps/sparc/atomic-machine.h
index a16f18fe57..b8c1e96eb4 100644
--- a/sysdeps/sparc/atomic-machine.h
+++ b/sysdeps/sparc/atomic-machine.h
@@ -19,9 +19,6 @@
 #ifndef _ATOMIC_MACHINE_H
 #define _ATOMIC_MACHINE_H	1
 
-/* XXX Is this actually correct?  */
-#define ATOMIC_EXCHANGE_USES_CAS     __HAVE_64B_ATOMICS
-
 #ifdef __sparc_v9__
 # define atomic_full_barrier() \
   __asm __volatile ("membar #LoadLoad | #LoadStore"			      \
diff --git a/sysdeps/x86/atomic-machine.h b/sysdeps/x86/atomic-machine.h
index 7c2ebfcee1..0681f57987 100644
--- a/sysdeps/x86/atomic-machine.h
+++ b/sysdeps/x86/atomic-machine.h
@@ -19,8 +19,6 @@
 #ifndef _X86_ATOMIC_MACHINE_H
 #define _X86_ATOMIC_MACHINE_H 1
 
-#define ATOMIC_EXCHANGE_USES_CAS	0
-
 #define atomic_spin_nop() __asm ("pause")
 
 #endif /* atomic-machine.h */