Re: drop volatile from __cpu_simplelock_t typedef

[Antti Kantee <pooka%iki.fi@localhost>]

On 26/06/15 14:51, Matt Thomas wrote:
> __cpu_simpe_lock_unlock concerns me without volatile.

Why?  Something to do with barriers?

> Also, many have loops that count on the variable changing.
> Without volatile those will become infinite loops.

Such as?  I can only think of the "C debugging version" of simple_lock ;)

Can't those be fixed by making them call __SIMPLELOCK_LOCKED_P()?  They 
arguably should have been doing that in the first place anyway.  Or are 
you worried that we won't be able to catch all of them?

> For RISC-V, I used the builtin C11-ish gcc atomics to implement
> the __cpu_simple_lock_t operations.  I just moved it to
> <sys/common_lock.h> so other ports could use it.

More MI code is always nice, but what's the relevance to this 
discussion?  <sys/common_lock.h> should work the same with or without 
volatile because the volatileness comes from atomic_store/exchange, no?


Anyway, I interpreted your reply as "sounds like a good idea, but there 
may be some problems".  If that's completely wrong, please be more explicit.