32 Thread support library [thread]

32.2 Requirements [thread.req]

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

32.2.5.5 Cpp17SharedLockable requirements [thread.req.lockable.shared]

A type L meets the Cpp17SharedLockable requirements if the following expressions are well-formed, have the specified semantics, and the expression m.try_­lock_­shared() has type bool (m denotes a value of type L):
m.lock_shared()
Effects: Blocks until a lock can be acquired for the current execution agent.
If an exception is thrown then a lock shall not have been acquired for the current execution agent.
m.try_lock_shared()
Effects: Attempts to acquire a lock for the current execution agent without blocking.
If an exception is thrown then a lock shall not have been acquired for the current execution agent.
Returns: true if the lock was acquired, false otherwise.
m.unlock_shared()
Preconditions: The current execution agent holds a shared lock on m.
Effects: Releases a shared lock on m held by the current execution agent.
Throws: Nothing.