• file
• revisions
• annotate
• diff
• comparison
• raw

ipc/chromium/src/base/atomicops_internals_arm_gcc.h@6474c204b198 (annotated)

ipc/chromium/src/base/atomicops_internals_arm_gcc.h

Wed, 31 Dec 2014 06:09:35 +0100

author

Michael Schloh von Bennewitz <michael@schloh.com>

date

Wed, 31 Dec 2014 06:09:35 +0100

changeset 0

6474c204b198

permissions

-rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

michael@0	1	// Copyright (c) 2009 The Chromium Authors. All rights reserved.
michael@0	2	// Use of this source code is governed by a BSD-style license that can be
michael@0	3	// found in the LICENSE file.
michael@0	4
michael@0	5	// This file is an internal atomic implementation, use base/atomicops.h instead.
michael@0	6	//
michael@0	7	// LinuxKernelCmpxchg and Barrier_AtomicIncrement are from Google Gears.
michael@0	8
michael@0	9	#ifndef BASE_ATOMICOPS_INTERNALS_ARM_GCC_H_
michael@0	10	#define BASE_ATOMICOPS_INTERNALS_ARM_GCC_H_
michael@0	11
michael@0	12	namespace base {
michael@0	13	namespace subtle {
michael@0	14
michael@0	15	// 0xffff0fc0 is the hard coded address of a function provided by
michael@0	16	// the kernel which implements an atomic compare-exchange. On older
michael@0	17	// ARM architecture revisions (pre-v6) this may be implemented using
michael@0	18	// a syscall. This address is stable, and in active use (hard coded)
michael@0	19	// by at least glibc-2.7 and the Android C library.
michael@0	20	typedef Atomic32 (*LinuxKernelCmpxchgFunc)(Atomic32 old_value,
michael@0	21	Atomic32 new_value,
michael@0	22	volatile Atomic32* ptr);
michael@0	23	LinuxKernelCmpxchgFunc pLinuxKernelCmpxchg __attribute__((weak)) =
michael@0	24	(LinuxKernelCmpxchgFunc) 0xffff0fc0;
michael@0	25
michael@0	26	typedef void (*LinuxKernelMemoryBarrierFunc)(void);
michael@0	27	LinuxKernelMemoryBarrierFunc pLinuxKernelMemoryBarrier __attribute__((weak)) =
michael@0	28	(LinuxKernelMemoryBarrierFunc) 0xffff0fa0;
michael@0	29
michael@0	30
michael@0	31	inline Atomic32 NoBarrier_CompareAndSwap(volatile Atomic32* ptr,
michael@0	32	Atomic32 old_value,
michael@0	33	Atomic32 new_value) {
michael@0	34	Atomic32 prev_value = *ptr;
michael@0	35	do {
michael@0	36	if (!pLinuxKernelCmpxchg(old_value, new_value,
michael@0	37	const_cast<Atomic32*>(ptr))) {
michael@0	38	return old_value;
michael@0	39	}
michael@0	40	prev_value = *ptr;
michael@0	41	} while (prev_value == old_value);
michael@0	42	return prev_value;
michael@0	43	}
michael@0	44
michael@0	45	inline Atomic32 NoBarrier_AtomicExchange(volatile Atomic32* ptr,
michael@0	46	Atomic32 new_value) {
michael@0	47	Atomic32 old_value;
michael@0	48	do {
michael@0	49	old_value = *ptr;
michael@0	50	} while (pLinuxKernelCmpxchg(old_value, new_value,
michael@0	51	const_cast<Atomic32*>(ptr)));
michael@0	52	return old_value;
michael@0	53	}
michael@0	54
michael@0	55	inline Atomic32 NoBarrier_AtomicIncrement(volatile Atomic32* ptr,
michael@0	56	Atomic32 increment) {
michael@0	57	return Barrier_AtomicIncrement(ptr, increment);
michael@0	58	}
michael@0	59
michael@0	60	inline Atomic32 Barrier_AtomicIncrement(volatile Atomic32* ptr,
michael@0	61	Atomic32 increment) {
michael@0	62	for (;;) {
michael@0	63	// Atomic exchange the old value with an incremented one.
michael@0	64	Atomic32 old_value = *ptr;
michael@0	65	Atomic32 new_value = old_value + increment;
michael@0	66	if (pLinuxKernelCmpxchg(old_value, new_value,
michael@0	67	const_cast<Atomic32*>(ptr)) == 0) {
michael@0	68	// The exchange took place as expected.
michael@0	69	return new_value;
michael@0	70	}
michael@0	71	// Otherwise, *ptr changed mid-loop and we need to retry.
michael@0	72	}
michael@0	73
michael@0	74	}
michael@0	75
michael@0	76	inline Atomic32 Acquire_CompareAndSwap(volatile Atomic32* ptr,
michael@0	77	Atomic32 old_value,
michael@0	78	Atomic32 new_value) {
michael@0	79	return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
michael@0	80	}
michael@0	81
michael@0	82	inline Atomic32 Release_CompareAndSwap(volatile Atomic32* ptr,
michael@0	83	Atomic32 old_value,
michael@0	84	Atomic32 new_value) {
michael@0	85	return NoBarrier_CompareAndSwap(ptr, old_value, new_value);
michael@0	86	}
michael@0	87
michael@0	88	inline void NoBarrier_Store(volatile Atomic32* ptr, Atomic32 value) {
michael@0	89	*ptr = value;
michael@0	90	}
michael@0	91
michael@0	92	inline void MemoryBarrier() {
michael@0	93	pLinuxKernelMemoryBarrier();
michael@0	94	}
michael@0	95
michael@0	96	inline void Acquire_Store(volatile Atomic32* ptr, Atomic32 value) {
michael@0	97	*ptr = value;
michael@0	98	MemoryBarrier();
michael@0	99	}
michael@0	100
michael@0	101	inline void Release_Store(volatile Atomic32* ptr, Atomic32 value) {
michael@0	102	MemoryBarrier();
michael@0	103	*ptr = value;
michael@0	104	}
michael@0	105
michael@0	106	inline Atomic32 NoBarrier_Load(volatile const Atomic32* ptr) {
michael@0	107	return *ptr;
michael@0	108	}
michael@0	109
michael@0	110	inline Atomic32 Acquire_Load(volatile const Atomic32* ptr) {
michael@0	111	Atomic32 value = *ptr;
michael@0	112	MemoryBarrier();
michael@0	113	return value;
michael@0	114	}
michael@0	115
michael@0	116	inline Atomic32 Release_Load(volatile const Atomic32* ptr) {
michael@0	117	MemoryBarrier();
michael@0	118	return *ptr;
michael@0	119	}
michael@0	120
michael@0	121	} // namespace base::subtle
michael@0	122	} // namespace base
michael@0	123
michael@0	124	#endif // BASE_ATOMICOPS_INTERNALS_ARM_GCC_H_