Mutex

Encapsulates an os specific exclusive lock.

Summary

Mutex	Encapsulates an os specific exclusive lock.
Copyright	This program is free software.
Files
C-kern/api/platform/sync/mutex.h	Header file of Mutex.
C-kern/platform/Linux/sync/mutex.c	Linux specific implementation Mutex Linuximpl.
Types
struct mutex_t	Exports mutex_t into global namespace.
Functions
test
unittest_platform_sync_mutex	Tests system thread functionality.
mutex_t	Implements a mutual exclusion lock.
lifetime
mutex_INIT_DEFAULT	Static initializer for mutex_t without error checking.
init_mutex	Initializer for a mutex with error checking.
free_mutex	Frees resources of mutex which is not in use.
change
lock_mutex	Locks a mutex.
unlock_mutex	Unlocks a previously locked mutex.
slock_mutex	Same as lock_mutex.
sunlock_mutex	Same as unlock_mutex.
inline implementation
slock_mutex	Implements mutex_t.slock_mutex.
sunlock_mutex	Implements mutex_t.sunlock_mutex.
KONFIG_SUBSYS
init_mutex	Implement mutex_t.init_mutex as a no op if !defined(KONFIG_SUBSYS_THREAD)
free_mutex	Implement mutex_t.free_mutex as a no op if !defined(KONFIG_SUBSYS_THREAD)
lock_mutex	Implement mutex_t.lock_mutex as a no op if !defined(KONFIG_SUBSYS_THREAD)
unlock_mutex	Implement mutex_t.unlock_mutex as a no op if !defined(KONFIG_SUBSYS_THREAD)

Copyright

This program is free software. You can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

Author

Files

C-kern/api/platform/sync/mutex.h

Header file of Mutex.

C-kern/platform/Linux/sync/mutex.c

Linux specific implementation Mutex Linuximpl.

Types

struct mutex_t

Exports mutex_t into global namespace.

Functions

Summary

test
unittest_platform_sync_mutex	Tests system thread functionality.

test

unittest_platform_sync_mutex

int unittest_platform_sync_mutex( void )

Tests system thread functionality.

mutex_t

typedef sys_mutex_t mutex_t

Implements a mutual exclusion lock. This thread safe object is used to protect a critical section of code against simultaneous execution by several threads. Use lock_mutex before entering a critical section of code and use unlock_mutex just before you leave it. This mutex can also be used between different processes.

Summary

lifetime
mutex_INIT_DEFAULT	Static initializer for mutex_t without error checking.
init_mutex	Initializer for a mutex with error checking.
free_mutex	Frees resources of mutex which is not in use.
change
lock_mutex	Locks a mutex.
unlock_mutex	Unlocks a previously locked mutex.
slock_mutex	Same as lock_mutex.
sunlock_mutex	Same as unlock_mutex.

lifetime

mutex_INIT_DEFAULT

#define mutex_INIT_DEFAULT sys_mutex_INIT_DEFAULT

Static initializer for mutex_t without error checking.

Following behaviour is guaranteed

1. No deadlock detection. 2. Locking it more than once without first unlocking it => DEADLOCK (waits indefinitely). 3. Unlocking a mutex locked by a different thread works. It is the same as if the thread which holds the lock calls unlock. 4. Unlocking an already unlocked mutex is unspecified. So never do it. 5. Works only within a single process as inter thread mutex.

init_mutex

int init_mutex( /*out*/mutex_t * mutex )

Initializer for a mutex with error checking.

Following behaviour is guaranteed

1. No deadlock detection. 2. Locking it more than once without first unlocking it returns error EDEADLK. 3. Unlocking a mutex locked by a different thread is prevented and returns error EPERM. 4. Unlocking an already unlocked mutex is prevented and returns error EPERM.

free_mutex

int free_mutex( mutex_t * mutex )

Frees resources of mutex which is not in use. Returns EBUSY if a thread holds a lock and nothing is freed.

change

lock_mutex

int lock_mutex( mutex_t * mutex )

Locks a mutex. If another thread holds the lock the calling thread waits until the lock is released. If a lock is acquired more than once a DEADLOCK results. If you try to lock a freed mutex EINVAL is returned.

unlock_mutex

int unlock_mutex( mutex_t * mutex )

Unlocks a previously locked mutex. Unlocking a mutex more than once is unspecified and may return success but corrupts internal counters. Unlocking a mutex which another thread has locked works as if the lock holder thread would call unlock. If you try to lock a freed mutex EINVAL is returned.

slock_mutex

void slock_mutex( mutex_t * mutex )

Same as lock_mutex. Except that an error leads to a system abort.

sunlock_mutex

void sunlock_mutex( mutex_t * mutex )

Same as unlock_mutex. Except that an error leads to a system abort.

inline implementation

Summary

slock_mutex	Implements mutex_t.slock_mutex.
sunlock_mutex	Implements mutex_t.sunlock_mutex.
KONFIG_SUBSYS
init_mutex	Implement mutex_t.init_mutex as a no op if !defined(KONFIG_SUBSYS_THREAD)
free_mutex	Implement mutex_t.free_mutex as a no op if !defined(KONFIG_SUBSYS_THREAD)
lock_mutex	Implement mutex_t.lock_mutex as a no op if !defined(KONFIG_SUBSYS_THREAD)
unlock_mutex	Implement mutex_t.unlock_mutex as a no op if !defined(KONFIG_SUBSYS_THREAD)

slock_mutex

#define slock_mutex( /*mutex_t * */mutex ) (assert(!lock_mutex(mutex))) ;

Implements mutex_t.slock_mutex.

sunlock_mutex

#define sunlock_mutex( /*mutex_t * */mutex ) (assert(!unlock_mutex(mutex))) ;

Implements mutex_t.sunlock_mutex.

KONFIG_SUBSYS

init_mutex

#define init_mutex( mutex ) (0)

Implement mutex_t.init_mutex as a no op if !defined(KONFIG_SUBSYS_THREAD)

free_mutex

#define free_mutex( mutex ) (0)

Implement mutex_t.free_mutex as a no op if !defined(KONFIG_SUBSYS_THREAD)

lock_mutex

#define lock_mutex( mutex ) (0)

Implement mutex_t.lock_mutex as a no op if !defined(KONFIG_SUBSYS_THREAD)

unlock_mutex

#define unlock_mutex( mutex ) (0)

Implement mutex_t.unlock_mutex as a no op if !defined(KONFIG_SUBSYS_THREAD)