[thread.req.lockable.general] (original) (raw)

32 Concurrency support library [thread]

32.2 Requirements [thread.req]

32.2.5 Requirements for Cpp17Lockable types [thread.req.lockable]

32.2.5.1 General [thread.req.lockable.general]

An execution agent is an entity such as a thread that may perform work in parallel with other execution agents.

[Note 1:

Implementations or users can introduce other kinds of agents such as processes or thread-pool tasks.

— _end note_]

The calling agent is determined by context, e.g., the calling thread that contains the call, and so on.

[Note 2:

Some lockable objects are “agent oblivious” in that they work for any execution agent model because they do not determine or store the agent's ID (e.g., an ordinary spin lock).

— _end note_]

[Note 3:

The nature of any lock ownership and any synchronization it entails are not part of these requirements.

— _end note_]

A lock on an object m is said to be

• a non-shared lock if it is acquired by a call tolock,try_lock,try_lock_for, ortry_lock_until on m, or
• a shared lock if it is acquired by a call tolock_shared,try_lock_shared,try_lock_shared_for, ortry_lock_shared_until on m.

[Note 4:

Only the method of lock acquisition is considered; the nature of any lock ownership is not part of these definitions.

— _end note_]