= The spin_lock library =

The [source:soft/giet_vm/giet_libs/spin_lock.c spin_lock.c] and [source:soft/giet_vm/giet_libs/spin_lock.h spin_lock.h] 
files define a user-level spin-lock service to obtain exclusive access to a shared resource in a parallel multi-tasks application.
Each lock (giet_lock_t object) occupies a complete 64 bytes cache line to avoid false sharing.
If the hardware architecture supports hardware cache coherence, it is recommanded to store the lock in a cachable segment architecture

 == Lock placement ==

The lock being shared by several tasks, is defined as a global variable in the application code.
It is possible to control precisely the placement of a specific lock by defining a specific vseg in the application mapping. 

 == Access functions ==

 * '''void lock_acquire( giet_lock_t * lock )'''
This blocking function uses an atomic LL/SC mechanism to take the lock, and return only when the lock has been successfully taken.

 * '''void lock_release( giet_lock_t * lock )'''
This function uses a simple SW to release the lock. It can be used for lock initialization.