Re: [Sbcl-devel] #ifdefing spin locks

[Perry E. M. <pe...@pi...>]

Christophe Rhodes <cs...@ca...> writes:
>> The #ifdefs are simple and are found all over the rest of the file
>> anyway. Can I use them?
>
> Just a thought -- might it be better to
>
>   (a) rename get_spinlock to get_sbcl_threads_spinlock (or something
>   that definitely signals that it should only be used to resolve
>   internal contention; not to interface with any other form of lock on
>   the platform, and (or "or", if get_spinlock is already idiomatic for
>   that)

Dunno. Perhaps. I think the existing names are reasonable, though I
suspect that instead of rolling one's own threads, using the pthreads
interface from the operating system would be far superior. Then one
can simply use the various pthreads_mutex calls to do mutual
exclusion, and one gets access to the OS's thread scheduler
interfaces.

That's a whole other story, though. Right now I just want to #ifdef
thread specific code in the non-threaded case.

>   (b) write a non-threaded version of get_spinlock() and
>   release_spinlock() on the x86, such that the appropriate one will be
>   chosen depending on LISP_FEATURE_SB_THREAD.  Then the operation of
>   get_spinlock() will be *word = value; or equivalent -- certainly
>   cheaper than lock cmpxchg.

There isn't any use in the code for spinlocks outside of thread
exclusion, so it isn't clear that we need a non-threaded version.

-- 
Perry E. Metzger		pe...@pi...