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This is a simple wrapper to bring atomic_bitops.txt into the RST world
until such a time as that file can be converted directly.”h]”hŒ¡SPDX-License-Identifier: GPL-2.0
This is a simple wrapper to bring atomic_bitops.txt into the RST world
until such a time as that file can be converted directly.”…””}”hh£sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1h¡hhhžhhŸŒM/var/lib/git/docbuild/linux/Documentation/core-api/wrappers/atomic_bitops.rst”h KubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒAtomic bitops”h]”hŒAtomic bitops”…””}”(hh»hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¹hh¶hžhhŸh³h KubhŒraw”“”)”}”(hŒ\footnotesize”h]”hŒ\footnotesize”…””}”hhËsbah}”(h]”h ]”h"]”h$]”h&]”Œformat”Œlatex”h±h²uh1hÉhŸh³h K	hh¶hžhubhŒliteral_block”“”)”}”(hX   =============
Atomic bitops
=============

While our bitmap_{}() functions are non-atomic, we have a number of operations
operating on single bits in a bitmap that are atomic.


API
---

The single bit operations are:

Non-RMW ops:

  test_bit()

RMW atomic operations without return value:

  {set,clear,change}_bit()
  clear_bit_unlock()

RMW atomic operations with return value:

  test_and_{set,clear,change}_bit()
  test_and_set_bit_lock()

Barriers:

  smp_mb__{before,after}_atomic()


All RMW atomic operations have a '__' prefixed variant which is non-atomic.


SEMANTICS
---------

Non-atomic ops:

In particular __clear_bit_unlock() suffers the same issue as atomic_set(),
which is why the generic version maps to clear_bit_unlock(), see atomic_t.txt.


RMW ops:

The test_and_{}_bit() operations return the original value of the bit.


ORDERING
--------

Like with atomic_t, the rule of thumb is:

 - non-RMW operations are unordered;

 - RMW operations that have no return value are unordered;

 - RMW operations that have a return value are fully ordered.

 - RMW operations that are conditional are fully ordered.

Except for a successful test_and_set_bit_lock() which has ACQUIRE semantics,
clear_bit_unlock() which has RELEASE semantics and test_bit_acquire which has
ACQUIRE semantics.

Since a platform only has a single means of achieving atomic operations
the same barriers as for atomic_t are used, see atomic_t.txt.

”h]”hX   =============
Atomic bitops
=============

While our bitmap_{}() functions are non-atomic, we have a number of operations
operating on single bits in a bitmap that are atomic.


API
---

The single bit operations are:

Non-RMW ops:

  test_bit()

RMW atomic operations without return value:

  {set,clear,change}_bit()
  clear_bit_unlock()

RMW atomic operations with return value:

  test_and_{set,clear,change}_bit()
  test_and_set_bit_lock()

Barriers:

  smp_mb__{before,after}_atomic()


All RMW atomic operations have a '__' prefixed variant which is non-atomic.


SEMANTICS
---------

Non-atomic ops:

In particular __clear_bit_unlock() suffers the same issue as atomic_set(),
which is why the generic version maps to clear_bit_unlock(), see atomic_t.txt.


RMW ops:

The test_and_{}_bit() operations return the original value of the bit.


ORDERING
--------

Like with atomic_t, the rule of thumb is:

 - non-RMW operations are unordered;

 - RMW operations that have no return value are unordered;

 - RMW operations that have a return value are fully ordered.

 - RMW operations that are conditional are fully ordered.

Except for a successful test_and_set_bit_lock() which has ACQUIRE semantics,
clear_bit_unlock() which has RELEASE semantics and test_bit_acquire which has
ACQUIRE semantics.

Since a platform only has a single means of achieving atomic operations
the same barriers as for atomic_t are used, see atomic_t.txt.

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