MutexLock< num_doors > Class Template Reference
#include <MutexLock.h>
Detailed Description
template<unsigned int num_doors>
class MutexLock< num_doors >
Implements a mutual exclusion lock using semaphores (SYSV style through SemaphoreManager).
Use this to prevent more than one process from accessing a data structure at the same time (which often leads to unpredictable and unexpected results)
The template parameter specifies the maximum number of different processes which need to be protected. This needs to be allocated ahead of time, as there doesn't seem to be a way to dynamically scale as needed without risking possible errors if two processes are both trying to set up at the same time. Also, by using a template parameter, all data structures are contained within the class's memory allocation, so no pointers are involved.
Locks in this class can be recursive or non-recursive, depending whether you call releaseAll() or unlock(). If you lock 5 times, then you need to call unlock() 5 times as well before it will be unlocked. However, if you lock 5 times, just one call to releaseAll() will undo all 5 levels of locking.
Just remember, unlock() releases one level. But releaseAll() completely unlocks.
Note that there is no check that the process doing the unlocking is the one that actually has the lock. Be careful about this.
- Warning:
- Doing mutual exclusion in software is tricky business, be careful about any modifications you make!
Definition at line 214 of file MutexLock.h.
Public Member Functions | |
| MutexLock () | |
| constructor, gets a new semaphore from the semaphore manager | |
| MutexLock (SemaphoreManager::semid_t semid) | |
| constructor, use this if you already have a semaphore id you want to use from semaphore manager | |
| ~MutexLock () | |
| destructor, releases semaphore back to semaphore manager | |
| void | lock (int id) |
| blocks until lock is achieved. This is done efficiently using a SysV style semaphore | |
| bool | try_lock (int id) |
| attempts to get a lock, returns true if it succeeds | |
| void | unlock () |
| releases one recursive lock-level from whoever has the current lock | |
| void | releaseAll () |
| completely unlocks, regardless of how many times a recursive lock has been obtained | |
| unsigned int | get_lock_level () const |
| returns the lockcount | |
| int | owner () const |
| returns the current owner's id | |
Protected Member Functions | |
| bool | isOwnerThread () |
| returns true if the current thread is the one which owns the lock | |
| virtual void | useResource (Resource::Data &) |
| marks the resource as in use | |
| virtual void | releaseResource (Resource::Data &) |
| releases the resource | |
Protected Attributes | |
| SemaphoreManager::semid_t | sem |
| the SysV semaphore number | |
| unsigned int | owner_index |
| holds the tekkotsu process id of the current lock owner | |
| pthread_t | owner_thread |
| holds a thread id for the owner thread | |
Private Member Functions | |
| MutexLock (const MutexLock &ml) | |
| copy constructor, do not call | |
| MutexLock & | operator= (const MutexLock &ml) |
| assignment, do not call | |
Friends | |
| class | MarkScope |
Constructor & Destructor Documentation
constructor, gets a new semaphore from the semaphore manager
Definition at line 217 of file MutexLock.h.
| MutexLock< num_doors >::MutexLock | ( | SemaphoreManager::semid_t | semid | ) | [inline] |
constructor, use this if you already have a semaphore id you want to use from semaphore manager
Definition at line 226 of file MutexLock.h.
destructor, releases semaphore back to semaphore manager
Definition at line 235 of file MutexLock.h.
| MutexLock< num_doors >::MutexLock | ( | const MutexLock< num_doors > & | ml | ) | [private] |
copy constructor, do not call
Member Function Documentation
| void MutexLock< num_doors >::lock | ( | int | id | ) | [inline] |
blocks until lock is achieved. This is done efficiently using a SysV style semaphore
You should pass some process-specific ID number as the input - just make sure no other process will be using the same value.
Definition at line 246 of file MutexLock.h.
Referenced by MotionManager::func_begin(), WorldStatePool::getCurrentWriteState(), MotionManager::InitAccess(), MotionManager::lock(), MessageQueue< MAX_UNREAD, MAX_RECEIVERS, MAX_SENDERS >::sendMessage(), and MutexLock< MAX_ACCESS >::useResource().
| bool MutexLock< num_doors >::try_lock | ( | int | id | ) | [inline] |
attempts to get a lock, returns true if it succeeds
You should pass some process-specific ID number as the input - just make sure no other process will be using the same value.
Definition at line 267 of file MutexLock.h.
Referenced by MotionManager::trylock().
| void MutexLock< num_doors >::unlock | ( | ) | [inline] |
releases one recursive lock-level from whoever has the current lock
Definition at line 289 of file MutexLock.h.
Referenced by WorldStatePool::doneWritingState(), MotionManager::func_end(), MotionManager::InitAccess(), MutexLock< MAX_ACCESS >::releaseResource(), and MotionManager::unlock().
| void MutexLock< num_doors >::releaseAll | ( | ) | [inline] |
completely unlocks, regardless of how many times a recursive lock has been obtained
Definition at line 307 of file MutexLock.h.
Referenced by MessageQueue< MAX_UNREAD, MAX_RECEIVERS, MAX_SENDERS >::sendMessage().
| unsigned int MutexLock< num_doors >::get_lock_level | ( | ) | const [inline] |
returns the lockcount
Definition at line 317 of file MutexLock.h.
Referenced by MessageQueue< MAX_UNREAD, MAX_RECEIVERS, MAX_SENDERS >::sendMessage().
| int MutexLock< num_doors >::owner | ( | ) | const [inline] |
returns the current owner's id
Definition at line 325 of file MutexLock.h.
Referenced by MutexLock< MAX_ACCESS >::try_lock().
| bool MutexLock< num_doors >::isOwnerThread | ( | ) | [inline, protected] |
returns true if the current thread is the one which owns the lock
Definition at line 329 of file MutexLock.h.
Referenced by MutexLock< MAX_ACCESS >::lock(), and MutexLock< MAX_ACCESS >::try_lock().
| virtual void MutexLock< num_doors >::useResource | ( | Resource::Data & | d | ) | [inline, protected, virtual] |
| virtual void MutexLock< num_doors >::releaseResource | ( | Resource::Data & | d | ) | [inline, protected, virtual] |
| MutexLock& MutexLock< num_doors >::operator= | ( | const MutexLock< num_doors > & | ml | ) | [private] |
assignment, do not call
Friends And Related Function Documentation
friend class MarkScope [friend] |
Definition at line 333 of file MutexLock.h.
Member Data Documentation
SemaphoreManager::semid_t MutexLock< num_doors >::sem [protected] |
the SysV semaphore number
Definition at line 341 of file MutexLock.h.
Referenced by MutexLock< MAX_ACCESS >::get_lock_level(), MutexLock< MAX_ACCESS >::lock(), MutexLock< MAX_ACCESS >::MutexLock(), MutexLock< MAX_ACCESS >::releaseAll(), MutexLock< MAX_ACCESS >::try_lock(), MutexLock< MAX_ACCESS >::unlock(), and MutexLock< MAX_ACCESS >::~MutexLock().
unsigned int MutexLock< num_doors >::owner_index [protected] |
holds the tekkotsu process id of the current lock owner
Definition at line 342 of file MutexLock.h.
Referenced by MutexLock< MAX_ACCESS >::get_lock_level(), MutexLock< MAX_ACCESS >::lock(), MutexLock< MAX_ACCESS >::owner(), MutexLock< MAX_ACCESS >::releaseAll(), MutexLock< MAX_ACCESS >::try_lock(), MutexLock< MAX_ACCESS >::unlock(), and MutexLock< MAX_ACCESS >::~MutexLock().
pthread_t MutexLock< num_doors >::owner_thread [protected] |
holds a thread id for the owner thread
Definition at line 343 of file MutexLock.h.
Referenced by MutexLock< MAX_ACCESS >::isOwnerThread(), MutexLock< MAX_ACCESS >::lock(), and MutexLock< MAX_ACCESS >::try_lock().
The documentation for this class was generated from the following file:
