Richard Thompson / MutexLocker

Mutex Locker utility class to lock/unlock mbed RTOS mutexes. Create and pass a mutex, it locks the mutex then unlocks it when destroyed.

Dependents:   SmartLight HelloThreadsYo

Mutex Locker

This utility class is most useful when you have an activity that needs to be protected by a mutex that has multiple return points.

You would normally do this:

Using standard mutex access

Mutex myMutex;

void do_some_stuff()
{
  myMutex.lock();
  /* Do Stuff */

  if (condition) {
    myMutex.unlock();
    return 0;
  }

  /* Call other method */
  int temp = other_method();  // Temp so can unlock after function returns

  myMutex.unlock();
  return temp;
}

However, it's very easy to miss one of the unlock points which would later freeze the application.

Debugging this kind of error can be very hard.

The same example using MutexLocker:

Using a MutexLocker

Mutex myMutex;

int do_some_stuff()
{
  MutexLocker locker(myMutex);
  /* Do Stuff */

  if (condition) {
    return 0;
  }
  /* Call other method */
  return other_method();
  /* Mutex unlocks itself here */
}

No matter where or how your method returns, the mutex will always be unlocked as the MutexLocker goes out of scope.

Diff: mutexlocker.h

Revision:
2:8bf85ca6ccee
Parent:
1:1a8b1de53954
Child:
3:aab6944f2ed3
--- a/mutexlocker.h	Thu Apr 10 22:06:40 2014 +0000
+++ b/mutexlocker.h	Thu Apr 10 22:14:23 2014 +0000
@@ -1,9 +1,14 @@
+/* (C) 2014 Richard Thompson (Tomo2k)
+This software is Apache 2.0 licenced for this to be reused.
+
+That said, it's trivial and rather obvious!
+*/
 #pragma once
 
 #include "rtos.h"
 
 
-//! Lock/Unlokc Mutex using variable scope.
+//! Lock/Unlock Mutex using variable scope.
 //! Ensures always unlocked regardless of method exit
 class MutexLocker
 {