[PATCH, newlib] Allow locking routine to be retargeted

[Sebastian Huber]

Hello Thomas,

On 23/11/16 15:38, Thomas Preudhomme wrote:
> Hi Sebastian,
>
> I was thinking on how to solve this issue and found two possible 
> solutions:
>
> 1) select size of lock at configure time
>
> Instead of being an enable/disable option the configure option could 
> take an integer value N that determine the size of lock, default being 
> the size of a pointer. The lock would then be defined as an array of N 
> integers.
>
> Pro: LOCK_INIT works, simpler & smaller change
> Cons: lock needs to be as big as the biggest lock among all the 
> platforms you want to target wasting a bit of space.
>
> 2) Remove static initialization of locks
>
> Remove all LOCK_INIT and add code as required to call lock_initialize 
> at start up time.
>
> Pro: you only pay the size for the lock you need (ie nothing except 
> empty functions in the single threaded case)
> Cons: much bigger work, start up cannot support multithread

3)

struct _lock;

typedef struct _lock *_LOCK_T;

#define __LOCK_INIT(class, lock) extern struct _lock _lock_ ## lock; class _LOCK_T lock = &_lock_ ## lock;

The OS must then provide struct _lock and storage for all statically initialized locks.

-- 
Sebastian Huber, embedded brains GmbH

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