0fec6b9d88
__atomic_cmpxchg and other related atomic operations did not provide memory barriers, which can be a problem for non-platform code that links against them when it runs on multi-core devices. This patch does two things to fix this: - It modifies the existing implementation of the functions that are exported by the C library to always provide full memory barriers. We need to keep them exported by the C library to prevent breaking existing application machine code. - It also modifies <sys/atomics.h> to only export always-inlined versions of the functions, to ensure that any application code compiled against the new header will not rely on the platform version of the functions. This ensure that said machine code will run properly on all multi-core devices. This is based on the GCC built-in sync primitives. The end result should be only slightly slower than the previous implementation. Note that the platform code does not use these functions at all. A previous patch completely removed their usage in the pthread and libstdc++ code. + rename arch-arm/bionic/atomics_arm.S to futex_arm.S + rename arch-x86/bionic/atomics_x86.S to futex_x86.S + remove arch-x86/include/sys/atomics.h which already provided inlined functions to the x86 platform. Change-Id: I752a594475090cf37fa926bb38209c2175dda539
112 lines
2.9 KiB
ArmAsm
112 lines
2.9 KiB
ArmAsm
/*
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* Copyright (C) 2008 The Android Open Source Project
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
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* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
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* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
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* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
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* OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
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* OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/linux-syscalls.h>
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#include <machine/asm.h>
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#include <machine/cpu-features.h>
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#define FUTEX_WAIT 0
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#define FUTEX_WAKE 1
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/* __futex_wait(*ftx, val, *timespec) */
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/* __futex_wake(*ftx, counter) */
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/* __futex_syscall3(*ftx, op, val) */
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/* __futex_syscall4(*ftx, op, val, *timespec) */
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.global __futex_wait
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.type __futex_wait, %function
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.global __futex_wake
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.type __futex_wake, %function
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.global __futex_syscall3
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.type __futex_syscall3, %function
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.global __futex_syscall4
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.type __futex_syscall4, %function
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#if __ARM_EABI__
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ENTRY(__futex_syscall3)
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stmdb sp!, {r4, r7}
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.save {r4, r7}
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ldr r7, =__NR_futex
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swi #0
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ldmia sp!, {r4, r7}
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bx lr
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END(__futex_syscall3)
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ENTRY(__futex_wait)
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stmdb sp!, {r4, r7}
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.save {r4, r7}
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mov r3, r2
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mov r2, r1
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mov r1, #FUTEX_WAIT
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ldr r7, =__NR_futex
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swi #0
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ldmia sp!, {r4, r7}
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bx lr
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END(__futex_wait)
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ENTRY(__futex_wake)
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.save {r4, r7}
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stmdb sp!, {r4, r7}
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mov r2, r1
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mov r1, #FUTEX_WAKE
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ldr r7, =__NR_futex
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swi #0
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ldmia sp!, {r4, r7}
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bx lr
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END(__futex_wake)
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#else
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ENTRY(__futex_syscall3)
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swi #__NR_futex
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bx lr
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END(__futex_syscall3)
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ENTRY(__futex_wait)
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mov r3, r2
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mov r2, r1
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mov r1, #FUTEX_WAIT
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swi #__NR_futex
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bx lr
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END(__futex_wait)
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ENTRY(__futex_wake)
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mov r2, r1
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mov r1, #FUTEX_WAKE
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swi #__NR_futex
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bx lr
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END(__futex_wake)
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#endif
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ENTRY(__futex_syscall4)
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b __futex_syscall3
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END(__futex_syscall4)
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