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Update ARM atomic operations
- From: Daniel Jacobowitz <drow at false dot org>
- To: libc-ports at sourceware dot org, pb at reciva dot com
- Date: Wed, 5 Oct 2005 12:49:02 -0400
- Subject: Update ARM atomic operations
This is the second of three patches to update the ARM port. This one
replaces atomicity.h, which hasn't been used in a long time, with
<bits/atomic.h>.
It preserves the same algorithms as the previous file; in particular, the
good enough but not quite atomic compare and swap algorithm. The NPTL
patches will include a completely atomic method which requires kernel
support. ARM v6 ldrex/strex support could be added to this file, if
desired.
OK to apply?
--
Daniel Jacobowitz
CodeSourcery, LLC
2005-10-05 Daniel Jacobowitz <dan@codesourcery.com>
* sysdeps/arm/atomicity.h: Delete.
* sysdeps/arm/bits/atomic.h: New file.
Index: glibc/ports/sysdeps/arm/atomicity.h
===================================================================
--- glibc.orig/ports/sysdeps/arm/atomicity.h 2001-07-06 00:55:47.000000000 -0400
+++ /dev/null 1970-01-01 00:00:00.000000000 +0000
@@ -1,87 +0,0 @@
-/* Low-level functions for atomic operations. ARM version.
- Copyright (C) 1997, 1998, 1999, 2000 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, write to the Free
- Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
- 02111-1307 USA. */
-
-#ifndef _ATOMICITY_H
-#define _ATOMICITY_H 1
-
-#include <inttypes.h>
-
-
-static inline int
-__attribute__ ((unused))
-exchange_and_add (volatile uint32_t *mem, int val)
-{
- int tmp1;
- int tmp2;
- int result;
- __asm__ ("\n"
- "0:\tldr\t%0,[%3]\n\t"
- "add\t%1,%0,%4\n\t"
- "swp\t%2,%1,[%3]\n\t"
- "cmp\t%0,%2\n\t"
- "swpne\t%1,%2,[%3]\n\t"
- "bne\t0b"
- : "=&r" (result), "=&r" (tmp1), "=&r" (tmp2)
- : "r" (mem), "r"(val)
- : "cc", "memory");
- return result;
-}
-
-static inline void
-__attribute__ ((unused))
-atomic_add (volatile uint32_t *mem, int val)
-{
- int tmp1;
- int tmp2;
- int tmp3;
- __asm__ ("\n"
- "0:\tldr\t%0,[%3]\n\t"
- "add\t%1,%0,%4\n\t"
- "swp\t%2,%1,[%3]\n\t"
- "cmp\t%0,%2\n\t"
- "swpne\t%1,%2,[%3]\n\t"
- "bne\t0b"
- : "=&r" (tmp1), "=&r" (tmp2), "=&r" (tmp3)
- : "r" (mem), "r"(val)
- : "cc", "memory");
-}
-
-static inline int
-__attribute__ ((unused))
-compare_and_swap (volatile long int *p, long int oldval, long int newval)
-{
- int result, tmp;
- __asm__ ("\n"
- "0:\tldr\t%1,[%2]\n\t"
- "mov\t%0,#0\n\t"
- "cmp\t%1,%4\n\t"
- "bne\t1f\n\t"
- "swp\t%0,%3,[%2]\n\t"
- "cmp\t%1,%0\n\t"
- "swpne\t%1,%0,[%2]\n\t"
- "bne\t0b\n\t"
- "mov\t%0,#1\n"
- "1:"
- : "=&r" (result), "=&r" (tmp)
- : "r" (p), "r" (newval), "r" (oldval)
- : "cc", "memory");
- return result;
-}
-
-#endif /* atomicity.h */
Index: glibc/ports/sysdeps/arm/bits/atomic.h
===================================================================
--- /dev/null 1970-01-01 00:00:00.000000000 +0000
+++ glibc/ports/sysdeps/arm/bits/atomic.h 2005-10-03 19:00:18.000000000 -0400
@@ -0,0 +1,101 @@
+/* Copyright (C) 2002, 2003, 2004, 2005 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, write to the Free
+ Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+ 02111-1307 USA. */
+
+#include <stdint.h>
+#include <sysdep.h>
+
+
+typedef int8_t atomic8_t;
+typedef uint8_t uatomic8_t;
+typedef int_fast8_t atomic_fast8_t;
+typedef uint_fast8_t uatomic_fast8_t;
+
+typedef int32_t atomic32_t;
+typedef uint32_t uatomic32_t;
+typedef int_fast32_t atomic_fast32_t;
+typedef uint_fast32_t uatomic_fast32_t;
+
+typedef intptr_t atomicptr_t;
+typedef uintptr_t uatomicptr_t;
+typedef intmax_t atomic_max_t;
+typedef uintmax_t uatomic_max_t;
+
+void __arm_link_error (void);
+
+#define atomic_exchange_acq(mem, newvalue) \
+ ({ __typeof (*mem) result; \
+ if (sizeof (*mem) == 1) \
+ __asm__ __volatile__ ("swpb %0, %1, [%2]" \
+ : "=&r,&r" (result) \
+ : "r,0" (newvalue), "r,r" (mem) : "memory"); \
+ else if (sizeof (*mem) == 4) \
+ __asm__ __volatile__ ("swp %0, %1, [%2]" \
+ : "=&r,&r" (result) \
+ : "r,0" (newvalue), "r,r" (mem) : "memory"); \
+ else \
+ { \
+ result = 0; \
+ abort (); \
+ } \
+ result; })
+
+/* Atomic compare and exchange. These sequences are not actually atomic;
+ there is a race if *MEM != OLDVAL and we are preempted between the two
+ swaps. However, they are very close to atomic, and are the best that a
+ pre-ARMv6 implementation can do without operating system support.
+ LinuxThreads has been using these sequences for many years. */
+
+#define __arch_compare_and_exchange_val_8_acq(mem, newval, oldval) \
+ ({ __typeof (oldval) result, tmp; \
+ __asm__ ("\n" \
+ "0:\tldr\t%1,[%2]\n\t" \
+ "cmp\t%1,%4\n\t" \
+ "movne\t%0,%1\n\t" \
+ "bne\t1f\n\t" \
+ "swpb\t%0,%3,[%2]\n\t" \
+ "cmp\t%1,%0\n\t" \
+ "swpbne\t%1,%0,[%2]\n\t" \
+ "bne\t0b\n\t" \
+ "1:" \
+ : "=&r" (result), "=&r" (tmp) \
+ : "r" (mem), "r" (newval), "r" (oldval) \
+ : "cc", "memory"); \
+ result; })
+
+#define __arch_compare_and_exchange_val_16_acq(mem, newval, oldval) \
+ ({ __arm_link_error (); oldval; })
+
+#define __arch_compare_and_exchange_val_32_acq(mem, newval, oldval) \
+ ({ __typeof (oldval) result, tmp; \
+ __asm__ ("\n" \
+ "0:\tldr\t%1,[%2]\n\t" \
+ "cmp\t%1,%4\n\t" \
+ "movne\t%0,%1\n\t" \
+ "bne\t1f\n\t" \
+ "swp\t%0,%3,[%2]\n\t" \
+ "cmp\t%1,%0\n\t" \
+ "swpne\t%1,%0,[%2]\n\t" \
+ "bne\t0b\n\t" \
+ "1:" \
+ : "=&r" (result), "=&r" (tmp) \
+ : "r" (mem), "r" (newval), "r" (oldval) \
+ : "cc", "memory"); \
+ result; })
+
+#define __arch_compare_and_exchange_val_64_acq(mem, newval, oldval) \
+ ({ __arm_link_error (); oldval; })