hi, two questions, mostly curious though:

On Sun, May 04, 2025 at 05:20:41PM +1000, David Gwynne wrote:
> PC_LOCK_INIT(9)            Kernel Developer's Manual           PC_LOCK_INIT(9)
> 
> NAME
>      pc_lock_init, pc_cons_enter, pc_cons_leave, pc_sprod_enter,
>      pc_sprod_leave, pc_mprod_enter, pc_mprod_leave, PC_LOCK_INITIALIZER -
>      producer/consumer locks
> 
> SYNOPSIS
>      #include <sys/pclock.h>
> 
>      void
>      pc_lock_init(struct pc_lock *pcl);
> 
>      void
>      pc_cons_enter(struct pc_lock *pcl, unsigned int *genp);

why not return gen as a return value?

>      int
>      pc_cons_leave(struct pc_lock *pcl, unsigned int *genp);
> 
>      unsigned int
>      pc_sprod_enter(struct pc_lock *pcl);
> 
>      void
>      pc_sprod_leave(struct pc_lock *pcl, unsigned int gen);
> 
>      unsigned int
>      pc_mprod_enter(struct pc_lock *pcl);
> 
>      void
>      pc_mprod_leave(struct pc_lock *pcl, unsigned int gen);
> 
>      PC_LOCK_INITIALIZER();

why do the callers have to store gen here? if i understand correctly,
this number cannot change while odd (pcl_gen & 1) in both cases?