all mutexes -> read-write locks?

[Julian Elischer]

Daniel Eischen wrote:
> On Sun, 1 Jun 2008, Ed Schouten wrote:
> 
>> Hello Julian,
>>
>> * Julian Elischer <julian at elischer.org> wrote:
>>> it has been mentioned several times that through the evolution of the
>>> locking primitives it has come to be that mutexes and exclusively
>>> acquired reader-writer locks are almost the same in terms of  overhead
>>> and that it might be a good move to define all mutexes to be
>>> actually just that.
>>>
>>> this would allow people to slowly go through the system, catching low
>>> hanging fruit by converting some of the mutex operations to reader
>>> acquisitions wherever a writer is not required, thus reducing general
>>> system contention.
>>>
>>> Is there any thought on this?  Last I heard jhb had confirmed that it
>>> was feasible..
>>
>> If this is going to be done, could we have mtx_* macro's pointing to the
>> proper read/write ops? I know, it's just names, but I think most novice
>> FreeBSD kernel hackers will almost instantaneously figure out what 'mtx'
>> stands for.
> 
> Yes, mutex (mtx) is known very well.
> 
> I don't think changing all mutex operations to rdlock operations
> is wise.  They are two different animals, regardless of their
> implementation.  Mutexes are very commonly used in device drivers,
> at least outside of FreeBSD.  And just because our current
> implementation of them are the same as rwlocks doesn't mean that
> it will always be the same in the future.
> 

so let's imagine that mutexes dissappear...
:-)