Mastering Embedded Linux Programming - Second Edition

Mutual exclusion

To write robust programs, you need to protect each shared resource with a mutex lock, and make sure that every code path that reads or writes the resource has locked the mutex first. If you apply this rule consistently, most of the problems should be solved. The ones that remain are associated with the fundamental behavior of mutexes. I will list them briefly here but will not go into detail:

• Deadlock: This occurs when mutexes become permanently locked. A classic situation is the deadly embrace in which two threads each require two mutexes and have managed to lock one of them but not the other. Each thread blocks, waiting for the lock the other has, and so they remain as they are. One simple rule to avoid the deadly embrace ...