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Use barriers and SMP-safe operations on ARM NPTL
- From: Daniel Jacobowitz <drow at false dot org>
- To: libc-ports at sourceware dot org
- Date: Sun, 1 Jun 2008 21:59:57 -0400
- Subject: Use barriers and SMP-safe operations on ARM NPTL
I've committed this updated version of the patch Zack posted last
year, which has been in our tree for some time. SWP is slow, and in
some cases not safe for SMP - I believe this is because it does not
interact correctly with ldrex/strex in the kernel helper, but I'm not
sure about that. Anyway, even on older generations of ARM chips swp
was never a speed demon; now that we don't need to rely on it, we
shouldn't.
--
Daniel Jacobowitz
CodeSourcery
2008-06-01 Paul Brook <paul@codesourcery.com>
Zack Weinberg <zack@codesourcery.com>
Daniel Jacobowitz <dan@codesourcery.com>
* sysdeps/arm/nptl/pthread_spin_lock.S,
sysdeps/arm/nptl/pthread_spin_trylock.S: Delete.
* sysdeps/arm/nptl/pthread_spin_lock.c,
sysdeps/arm/nptl/pthread_spin_trylock.c: New files using
atomic_compare_and_exchange_val_acq to take spinlocks.
* sysdeps/unix/sysv/linux/arm/nptl/bits/atomic.h (lll_trylock,
lll_cond_trylock): Use atomic_compare_and_exchange_val_acq.
(__lll_trylock, __lll_cond_trylock): Delete.
* sysdeps/unix/sysv/linux/arm/nptl/bits/atomic.h
(atomic_exchange_acq): Delete.
(atomic_full_barrier): Define.
(__arch_compare_and_exchange_val_32_acq): Use named operands.
* sysdeps/unix/sysv/linux/arm/eabi/configure.in: Update
arch_minimum_kernel to 2.6.16.
* sysdeps/unix/sysv/linux/arm/eabi/configure: Regenerated.
Index: sysdeps/arm/nptl/pthread_spin_lock.S
===================================================================
RCS file: sysdeps/arm/nptl/pthread_spin_lock.S
diff -N sysdeps/arm/nptl/pthread_spin_lock.S
--- sysdeps/arm/nptl/pthread_spin_lock.S 16 Nov 2005 19:03:42 -0000 1.1
+++ /dev/null 1 Jan 1970 00:00:00 -0000
@@ -1,31 +0,0 @@
-/* Copyright (C) 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 <sysdep.h>
-
- .text
- .align 4
-
-ENTRY (pthread_spin_lock)
- mov r1, #1
-1: swp r2, r1, [r0]
- teq r2, #0
- bne 1b
- mov r0, #0
- PSEUDO_RET_NOERRNO
-END (pthread_spin_lock)
Index: sysdeps/arm/nptl/pthread_spin_lock.c
===================================================================
RCS file: sysdeps/arm/nptl/pthread_spin_lock.c
diff -N sysdeps/arm/nptl/pthread_spin_lock.c
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ sysdeps/arm/nptl/pthread_spin_lock.c 2 Jun 2008 01:47:56 -0000
@@ -0,0 +1,30 @@
+/* Copyright (C) 2008 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 <atomic.h>
+#include "pthreadP.h"
+
+int
+pthread_spin_lock (pthread_spinlock_t *lock)
+{
+ while (atomic_compare_and_exchange_val_acq (lock, 1, 0) != 0)
+ while (*lock != 0)
+ ;
+
+ return 0;
+}
Index: sysdeps/arm/nptl/pthread_spin_trylock.S
===================================================================
RCS file: sysdeps/arm/nptl/pthread_spin_trylock.S
diff -N sysdeps/arm/nptl/pthread_spin_trylock.S
--- sysdeps/arm/nptl/pthread_spin_trylock.S 16 Nov 2005 19:03:42 -0000 1.1
+++ /dev/null 1 Jan 1970 00:00:00 -0000
@@ -1,34 +0,0 @@
-/* Copyright (C) 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. */
-
-#define _ERRNO_H 1
-#include <bits/errno.h>
-
-#include <sysdep.h>
-
- .text
- .align 4
-
-ENTRY (pthread_spin_trylock)
- mov r1, #1
- swp r2, r1, [r0]
- teq r2, #0
- moveq r0, #0
- movne r0, #EBUSY
- PSEUDO_RET_NOERRNO
-END (pthread_spin_trylock)
Index: sysdeps/arm/nptl/pthread_spin_trylock.c
===================================================================
RCS file: sysdeps/arm/nptl/pthread_spin_trylock.c
diff -N sysdeps/arm/nptl/pthread_spin_trylock.c
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ sysdeps/arm/nptl/pthread_spin_trylock.c 2 Jun 2008 01:47:56 -0000
@@ -0,0 +1,27 @@
+/* Copyright (C) 2008 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 <errno.h>
+#include <atomic.h>
+#include "pthreadP.h"
+
+int
+pthread_spin_trylock (pthread_spinlock_t *lock)
+{
+ return atomic_compare_and_exchange_val_acq (lock, 1, 0) ? EBUSY : 0;
+}
Index: sysdeps/unix/sysv/linux/arm/nptl/lowlevellock.h
===================================================================
RCS file: /cvs/glibc/ports/sysdeps/unix/sysv/linux/arm/nptl/lowlevellock.h,v
retrieving revision 1.6
diff -u -p -r1.6 lowlevellock.h
--- sysdeps/unix/sysv/linux/arm/nptl/lowlevellock.h 12 Sep 2007 12:57:25 -0000 1.6
+++ sysdeps/unix/sysv/linux/arm/nptl/lowlevellock.h 2 Jun 2008 01:47:57 -0000
@@ -126,43 +126,11 @@
})
-static inline int __attribute__((always_inline))
-__lll_trylock (int *futex)
-{
- int flag = 1, old;
- asm volatile (
- "\tswp %[old], %[flag], [%[futex]] @ try to take the lock\n"
- "\tcmp %[old], #1 @ check old lock value\n"
- "\tmovlo %[flag], #0 @ if we got it, return 0\n"
- "\tswphi %[flag], %[old], [%[futex]] @ if it was contested,\n"
- " @ restore the contested flag,\n"
- " @ and check whether that won."
- : [futex] "+&r" (futex), [flag] "+&r" (flag), [old] "=&r" (old)
- : : "memory" );
-
- return flag;
-}
-#define lll_trylock(lock) __lll_trylock (&(lock))
-
-
-static inline int __attribute__((always_inline))
-__lll_cond_trylock (int *futex)
-{
- int flag = 2, old;
- asm volatile (
- "\tswp %[old], %[flag], [%[futex]] @ try to take the lock\n"
- "\tcmp %[old], #1 @ check old lock value\n"
- "\tmovlo %[flag], #0 @ if we got it, return 0\n"
- "\tswphi %[flag], %[old], [%[futex]] @ if it was contested,\n"
- " @ restore the contested flag,\n"
- " @ and check whether that won."
- : [futex] "+&r" (futex), [flag] "+&r" (flag), [old] "=&r" (old)
- : : "memory" );
-
- return flag;
-}
-#define lll_cond_trylock(lock) __lll_cond_trylock (&(lock))
+#define lll_trylock(lock) \
+ atomic_compare_and_exchange_val_acq(&(lock), 1, 0)
+#define lll_cond_trylock(lock) \
+ atomic_compare_and_exchange_val_acq(&(lock), 2, 0)
#define __lll_robust_trylock(futex, id) \
(atomic_compare_and_exchange_val_acq (futex, id, 0) != 0)
Index: sysdeps/unix/sysv/linux/arm/nptl/bits/atomic.h
===================================================================
RCS file: /cvs/glibc/ports/sysdeps/unix/sysv/linux/arm/nptl/bits/atomic.h,v
retrieving revision 1.1
diff -u -p -r1.1 atomic.h
--- sysdeps/unix/sysv/linux/arm/nptl/bits/atomic.h 16 Nov 2005 19:03:42 -0000 1.1
+++ sysdeps/unix/sysv/linux/arm/nptl/bits/atomic.h 2 Jun 2008 01:47:57 -0000
@@ -37,22 +37,12 @@ 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; })
+#define atomic_full_barrier() \
+ __asm__ __volatile__ \
+ ("mov\tip, #0xffff0fff\n\t" \
+ "mov\tlr, pc\n\t" \
+ "add\tpc, ip, #(0xffff0fa0 - 0xffff0fff)" \
+ : : : "ip", "lr", "cc", "memory");
/* Atomic compare and exchange. This sequence relies on the kernel to
provide a compare and exchange operation which is atomic on the
@@ -76,18 +66,19 @@ void __arm_link_error (void);
register __typeof (oldval) a_tmp asm ("r3"); \
register __typeof (oldval) a_oldval2 asm ("r4") = (oldval); \
__asm__ __volatile__ \
- ("0:\tldr\t%1,[%3]\n\t" \
- "cmp\t%1, %4\n\t" \
+ ("0:\tldr\t%[tmp],[%[ptr]]\n\t" \
+ "cmp\t%[tmp], %[old2]\n\t" \
"bne\t1f\n\t" \
- "mov\t%0, %4\n\t" \
- "mov\t%1, #0xffff0fff\n\t" \
+ "mov\t%[old], %[old2]\n\t" \
+ "mov\t%[tmp], #0xffff0fff\n\t" \
"mov\tlr, pc\n\t" \
- "add\tpc, %1, #(0xffff0fc0 - 0xffff0fff)\n\t" \
+ "add\tpc, %[tmp], #(0xffff0fc0 - 0xffff0fff)\n\t" \
"bcc\t0b\n\t" \
- "mov\t%1, %4\n\t" \
+ "mov\t%[tmp], %[old2]\n\t" \
"1:" \
- : "=&r" (a_oldval), "=&r" (a_tmp) \
- : "r" (a_newval), "r" (a_ptr), "r" (a_oldval2) \
+ : [old] "=&r" (a_oldval), [tmp] "=&r" (a_tmp) \
+ : [new] "r" (a_newval), [ptr] "r" (a_ptr), \
+ [old2] "r" (a_oldval2) \
: "ip", "lr", "cc", "memory"); \
a_tmp; })
Index: sysdeps/unix/sysv/linux/arm/eabi/configure
===================================================================
RCS file: /cvs/glibc/ports/sysdeps/unix/sysv/linux/arm/eabi/configure,v
retrieving revision 1.2
diff -u -p -r1.2 configure
--- sysdeps/unix/sysv/linux/arm/eabi/configure 16 Nov 2005 18:08:52 -0000 1.2
+++ sysdeps/unix/sysv/linux/arm/eabi/configure 2 Jun 2008 01:56:17 -0000
@@ -1,5 +1,5 @@
# This file is generated from configure.in by Autoconf. DO NOT EDIT!
# Local configure fragment for sysdeps/unix/sysv/linux/arm/eabi.
-arch_minimum_kernel=2.6.14
+arch_minimum_kernel=2.6.16
libc_cv_gcc_unwind_find_fde=no
Index: sysdeps/unix/sysv/linux/arm/eabi/configure.in
===================================================================
RCS file: /cvs/glibc/ports/sysdeps/unix/sysv/linux/arm/eabi/configure.in,v
retrieving revision 1.2
diff -u -p -r1.2 configure.in
--- sysdeps/unix/sysv/linux/arm/eabi/configure.in 16 Nov 2005 18:08:52 -0000 1.2
+++ sysdeps/unix/sysv/linux/arm/eabi/configure.in 2 Jun 2008 01:56:17 -0000
@@ -1,5 +1,5 @@
GLIBC_PROVIDES dnl See aclocal.m4 in the top level source directory.
# Local configure fragment for sysdeps/unix/sysv/linux/arm/eabi.
-arch_minimum_kernel=2.6.14
+arch_minimum_kernel=2.6.16
libc_cv_gcc_unwind_find_fde=no