#include <userver/engine/shared_mutex.hpp>

Detailed Description

std::shared_mutex replacement for asynchronous tasks.

Ignores task cancellations (succeeds even if the current task is cancelled).

Writers (unique locks) have priority over readers (shared locks), thus new shared lock waits for the pending writes to finish, which in turn waits for existing existing shared locks to unlock first.

Example usage:

 
    constexpr auto kTestString = "123";
 
    engine::SharedMutex mutex;
    std::string data;
    {
        std::lock_guard<engine::SharedMutex> lock(mutex);
        // accessing the data under the mutex for writing
        data = kTestString;
    }
 
    {
        std::shared_lock<engine::SharedMutex> lock(mutex);
        // accessing the data under the mutex for reading,
        // data cannot be changed
        const auto& x = data;
        ASSERT_EQ(x, kTestString);
    }

See also: Synchronization Primitives

Definition at line 29 of file shared_mutex.hpp.

Public Member Functions
	SharedMutex (const SharedMutex &)=delete

	SharedMutex (SharedMutex &&)=delete

SharedMutex &	operator= (const SharedMutex &)=delete

SharedMutex &	operator= (SharedMutex &&)=delete

void	lock ()

void	unlock ()

bool	try_lock ()

template<typename Rep , typename Period >
bool	try_lock_for (const std::chrono::duration< Rep, Period > &)

template<typename Clock , typename Duration >
bool	try_lock_until (const std::chrono::time_point< Clock, Duration > &)

bool	try_lock_until (Deadline deadline)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

void	lock_shared ()

void	unlock_shared ()

bool	try_lock_shared ()

template<typename Rep , typename Period >
bool	try_lock_shared_for (const std::chrono::duration< Rep, Period > &)

template<typename Clock , typename Duration >
bool	try_lock_shared_until (const std::chrono::time_point< Clock, Duration > &)

bool	try_lock_shared_until (Deadline deadline)
	This is an overloaded member function, provided for convenience. It differs from the above function only in what argument(s) it accepts.

Member Function Documentation

◆ lock()

void engine::SharedMutex::lock ( )

Locks the mutex for unique ownership. Blocks current coroutine if the mutex is locked by another coroutine for reading or writing.

Note: The method waits for the mutex even if the current task is cancelled.

◆ lock_shared()

void engine::SharedMutex::lock_shared ( )

Locks the mutex for shared ownership. Blocks current coroutine if the mutex is locked by another coroutine for reading or writing.

Note: The method waits for the mutex even if the current task is cancelled.

◆ try_lock()

bool engine::SharedMutex::try_lock ( )

Tries to lock the mutex for unique ownership without blocking the coroutine, returns true if succeeded.

◆ try_lock_for()

template<typename Rep , typename Period >

bool engine::SharedMutex::try_lock_for ( const std::chrono::duration< Rep, Period > & duration )

Tries to lock the mutex for unique ownership in specified duration. Blocks current coroutine if the mutex is locked by another coroutine up to the provided duration.

Returns: true if the locking succeeded

Definition at line 139 of file shared_mutex.hpp.

◆ try_lock_shared()

bool engine::SharedMutex::try_lock_shared ( )

Tries to lock the mutex for shared ownership without blocking the coroutine, returns true if succeeded.

◆ try_lock_shared_for()

template<typename Rep , typename Period >

bool engine::SharedMutex::try_lock_shared_for ( const std::chrono::duration< Rep, Period > & duration )

Tries to lock the mutex for shared ownership in specified duration. Blocks current coroutine if the mutex is locked by another coroutine up to the provided duration.

Returns: true if the locking succeeded

Definition at line 144 of file shared_mutex.hpp.

◆ try_lock_shared_until()

template<typename Clock , typename Duration >

bool engine::SharedMutex::try_lock_shared_until ( const std::chrono::time_point< Clock, Duration > & until )

Tries to lock the mutex for shared ownership till specified time point. Blocks current coroutine if the mutex is locked by another coroutine up to the provided duration.

Returns: true if the locking succeeded

Definition at line 154 of file shared_mutex.hpp.

◆ try_lock_until()

template<typename Clock , typename Duration >

bool engine::SharedMutex::try_lock_until ( const std::chrono::time_point< Clock, Duration > & until )

Tries to lock the mutex for unique ownership till specified time point. Blocks current coroutine if the mutex is locked by another coroutine up to the provided duration.

Returns: true if the locking succeeded

Definition at line 149 of file shared_mutex.hpp.

◆ unlock()

void engine::SharedMutex::unlock ( )

Unlocks the mutex for unique ownership. Before calling this method the the mutex should be locked for unique ownership by current coroutine.

Note: the order of coroutines to unblock is unspecified. Any code assuming any specific order (e.g. FIFO) is incorrect and should be fixed.

◆ unlock_shared()

void engine::SharedMutex::unlock_shared ( )

Unlocks the mutex for shared ownership. Before calling this method the mutex should be locked for shared ownership by current coroutine.

Note: the order of coroutines to unblock is unspecified. Any code assuming any specific order (e.g. FIFO) is incorrect and should be fixed.

The documentation for this class was generated from the following file:

userver/engine/shared_mutex.hpp