atomic_arm.go

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  //go:build arm
     6  
     7  package atomic
     8  
     9  import (
    10  	"internal/cpu"
    11  	"unsafe"
    12  )
    13  
    14  const (
    15  	offsetARMHasV7Atomics = unsafe.Offsetof(cpu.ARM.HasV7Atomics)
    16  )
    17  
    18  // Export some functions via linkname to assembly in sync/atomic.
    19  //
    20  //go:linkname Xchg
    21  //go:linkname Xchguintptr
    22  //go:linkname Xadd
    23  
    24  type spinlock struct {
    25  	v uint32
    26  }
    27  
    28  //go:nosplit
    29  func (l *spinlock) lock() {
    30  	for {
    31  		if Cas(&l.v, 0, 1) {
    32  			return
    33  		}
    34  	}
    35  }
    36  
    37  //go:nosplit
    38  func (l *spinlock) unlock() {
    39  	Store(&l.v, 0)
    40  }
    41  
    42  var locktab [57]struct {
    43  	l   spinlock
    44  	pad [cpu.CacheLinePadSize - unsafe.Sizeof(spinlock{})]byte
    45  }
    46  
    47  func addrLock(addr *uint64) *spinlock {
    48  	return &locktab[(uintptr(unsafe.Pointer(addr))>>3)%uintptr(len(locktab))].l
    49  }
    50  
    51  // Atomic add and return new value.
    52  //
    53  //go:nosplit
    54  func Xadd(val *uint32, delta int32) uint32 {
    55  	for {
    56  		oval := *val
    57  		nval := oval + uint32(delta)
    58  		if Cas(val, oval, nval) {
    59  			return nval
    60  		}
    61  	}
    62  }
    63  
    64  //go:noescape
    65  func Xadduintptr(ptr *uintptr, delta uintptr) uintptr
    66  
    67  //go:nosplit
    68  func Xchg(addr *uint32, v uint32) uint32 {
    69  	for {
    70  		old := *addr
    71  		if Cas(addr, old, v) {
    72  			return old
    73  		}
    74  	}
    75  }
    76  
    77  //go:noescape
    78  func Xchg8(addr *uint8, v uint8) uint8
    79  
    80  //go:nosplit
    81  func Xchguintptr(addr *uintptr, v uintptr) uintptr {
    82  	return uintptr(Xchg((*uint32)(unsafe.Pointer(addr)), uint32(v)))
    83  }
    84  
    85  // Not noescape -- it installs a pointer to addr.
    86  func StorepNoWB(addr unsafe.Pointer, v unsafe.Pointer)
    87  
    88  //go:noescape
    89  func Store(addr *uint32, v uint32)
    90  
    91  //go:noescape
    92  func StoreRel(addr *uint32, v uint32)
    93  
    94  //go:noescape
    95  func StoreReluintptr(addr *uintptr, v uintptr)
    96  
    97  //go:nosplit
    98  func goCas64(addr *uint64, old, new uint64) bool {
    99  	if uintptr(unsafe.Pointer(addr))&7 != 0 {
   100  		*(*int)(nil) = 0 // crash on unaligned uint64
   101  	}
   102  	_ = *addr // if nil, fault before taking the lock
   103  	var ok bool
   104  	addrLock(addr).lock()
   105  	if *addr == old {
   106  		*addr = new
   107  		ok = true
   108  	}
   109  	addrLock(addr).unlock()
   110  	return ok
   111  }
   112  
   113  //go:nosplit
   114  func goXadd64(addr *uint64, delta int64) uint64 {
   115  	if uintptr(unsafe.Pointer(addr))&7 != 0 {
   116  		*(*int)(nil) = 0 // crash on unaligned uint64
   117  	}
   118  	_ = *addr // if nil, fault before taking the lock
   119  	var r uint64
   120  	addrLock(addr).lock()
   121  	r = *addr + uint64(delta)
   122  	*addr = r
   123  	addrLock(addr).unlock()
   124  	return r
   125  }
   126  
   127  //go:nosplit
   128  func goXchg64(addr *uint64, v uint64) uint64 {
   129  	if uintptr(unsafe.Pointer(addr))&7 != 0 {
   130  		*(*int)(nil) = 0 // crash on unaligned uint64
   131  	}
   132  	_ = *addr // if nil, fault before taking the lock
   133  	var r uint64
   134  	addrLock(addr).lock()
   135  	r = *addr
   136  	*addr = v
   137  	addrLock(addr).unlock()
   138  	return r
   139  }
   140  
   141  //go:nosplit
   142  func goLoad64(addr *uint64) uint64 {
   143  	if uintptr(unsafe.Pointer(addr))&7 != 0 {
   144  		*(*int)(nil) = 0 // crash on unaligned uint64
   145  	}
   146  	_ = *addr // if nil, fault before taking the lock
   147  	var r uint64
   148  	addrLock(addr).lock()
   149  	r = *addr
   150  	addrLock(addr).unlock()
   151  	return r
   152  }
   153  
   154  //go:nosplit
   155  func goStore64(addr *uint64, v uint64) {
   156  	if uintptr(unsafe.Pointer(addr))&7 != 0 {
   157  		*(*int)(nil) = 0 // crash on unaligned uint64
   158  	}
   159  	_ = *addr // if nil, fault before taking the lock
   160  	addrLock(addr).lock()
   161  	*addr = v
   162  	addrLock(addr).unlock()
   163  }
   164  
   165  //go:noescape
   166  func Or8(addr *uint8, v uint8)
   167  
   168  //go:nosplit
   169  func goOr8(addr *uint8, v uint8) {
   170  	// Align down to 4 bytes and use 32-bit CAS.
   171  	addr32 := (*uint32)(unsafe.Pointer(uintptr(unsafe.Pointer(addr)) &^ 3))
   172  	word := uint32(v) << ((uintptr(unsafe.Pointer(addr)) & 3) * 8) // little endian
   173  	for {
   174  		old := *addr32
   175  		if Cas(addr32, old, old|word) {
   176  			return
   177  		}
   178  	}
   179  }
   180  
   181  //go:noescape
   182  func And8(addr *uint8, v uint8)
   183  
   184  //go:nosplit
   185  func goAnd8(addr *uint8, v uint8) {
   186  	// Align down to 4 bytes and use 32-bit CAS.
   187  	addr32 := (*uint32)(unsafe.Pointer(uintptr(unsafe.Pointer(addr)) &^ 3))
   188  	word := uint32(v) << ((uintptr(unsafe.Pointer(addr)) & 3) * 8)    // little endian
   189  	mask := uint32(0xFF) << ((uintptr(unsafe.Pointer(addr)) & 3) * 8) // little endian
   190  	word |= ^mask
   191  	for {
   192  		old := *addr32
   193  		if Cas(addr32, old, old&word) {
   194  			return
   195  		}
   196  	}
   197  }
   198  
   199  //go:nosplit
   200  func Or(addr *uint32, v uint32) {
   201  	for {
   202  		old := *addr
   203  		if Cas(addr, old, old|v) {
   204  			return
   205  		}
   206  	}
   207  }
   208  
   209  //go:nosplit
   210  func And(addr *uint32, v uint32) {
   211  	for {
   212  		old := *addr
   213  		if Cas(addr, old, old&v) {
   214  			return
   215  		}
   216  	}
   217  }
   218  
   219  //go:nosplit
   220  func armcas(ptr *uint32, old, new uint32) bool
   221  
   222  //go:noescape
   223  func Load(addr *uint32) uint32
   224  
   225  // NO go:noescape annotation; *addr escapes if result escapes (#31525)
   226  func Loadp(addr unsafe.Pointer) unsafe.Pointer
   227  
   228  //go:noescape
   229  func Load8(addr *uint8) uint8
   230  
   231  //go:noescape
   232  func LoadAcq(addr *uint32) uint32
   233  
   234  //go:noescape
   235  func LoadAcquintptr(ptr *uintptr) uintptr
   236  
   237  //go:noescape
   238  func Cas64(addr *uint64, old, new uint64) bool
   239  
   240  //go:noescape
   241  func CasRel(addr *uint32, old, new uint32) bool
   242  
   243  //go:noescape
   244  func Xadd64(addr *uint64, delta int64) uint64
   245  
   246  //go:noescape
   247  func Xchg64(addr *uint64, v uint64) uint64
   248  
   249  //go:noescape
   250  func Load64(addr *uint64) uint64
   251  
   252  //go:noescape
   253  func Store8(addr *uint8, v uint8)
   254  
   255  //go:noescape
   256  func Store64(addr *uint64, v uint64)
   257
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