svn commit: r335879 - in head/sys: conf kern sys

[Mark Johnston]

On Tue, Jul 03, 2018 at 01:55:10AM +0000, Matt Macy wrote:
> Author: mmacy
> Date: Tue Jul  3 01:55:09 2018
> New Revision: 335879
> URL: https://svnweb.freebsd.org/changeset/base/335879
> 
> Log:
>   make critical_{enter, exit} inline
>   
>   Avoid pulling in all of the <sys/proc.h> dependencies by
>   automatically generating a stripped down thread_lite exporting
>   only the fields of interest. The field declarations are type checked
>   against the original and the offsets of the generated result is
>   automatically checked.
>   
>   kib has expressed disagreement and would have preferred to simply
>   use genassym style offsets (which loses type check enforcement).
>   jhb has expressed dislike of it due to header pollution and a
>   duplicate structure. He would have preferred to just have defined
>   thread in _thread.h. Nonetheless, he admits that this is the only
>   viable solution at the moment.
>   
>   The impetus for this came from mjg's D15331:
>   "Inline critical_enter/exit for amd64"
>   
>   Reviewed by: jeff
>   Differential Revision: https://reviews.freebsd.org/D16078
> 
> [...]
> +#if defined(KLD_MODULE) || defined(KTR_CRITICAL) || !defined(_KERNEL) || defined(GENOFFSET)
> +#define critical_enter() critical_enter_KBI()
> +#define critical_exit() critical_exit_KBI()
> +#else
> +static __inline void
> +critical_enter(void)
> +{
> +	struct thread_lite *td;
> +
> +	td = (struct thread_lite *)curthread;
> +	td->td_critnest++;

Don't we need a compiler barrier here?

> +}
> +
> +static __inline void
> +critical_exit(void)
> +{
> +	struct thread_lite *td;
> +
> +	td = (struct thread_lite *)curthread;
> +	KASSERT(td->td_critnest != 0,
> +	    ("critical_exit: td_critnest == 0"));
> +	td->td_critnest--;
> +	__compiler_membar();
> +	if (__predict_false(td->td_owepreempt))
> +		critical_exit_preempt();
> +
> +}
> +#endif
> +
> +
>  #ifdef  EARLY_PRINTF
>  typedef void early_putc_t(int ch);
>  extern early_putc_t *early_putc;
>