Re: [PATCH gnumach] Enable MACH_HOST and fix non-addressable bitfields

[Samuel Thibault]

Damien Zammit, le dim. 11 févr. 2024 10:55:26 +0000, a ecrit:
> >> diff --git a/kern/task.h b/kern/task.h
> >> index dec3a530..27970620 100644
> >> --- a/kern/task.h
> >> +++ b/kern/task.h
> >> @@ -61,11 +61,11 @@ struct task {
> >>    decl_simple_lock_data(,lock)    /* Task's lock */
> >>    int             ref_count;      /* Number of references to me */
> >>
> >> -  /* Flags */
> >> -  unsigned int    active:1,       /* Task has not been terminated */
> >> -  /* boolean_t */ may_assign:1,   /* can assigned pset be changed? */
> >> -                  assign_active:1,        /* waiting for may_assign */
> >> -                  essential:1;    /* Is this task essential for the 
> >> system? */
> >> +  /* Addressable flags */
> >> +  unsigned char   active;         /* Task has not been terminated */
> >> +  unsigned char   may_assign;     /* can assigned pset be changed? */
> >> +  unsigned char   assign_active;  /* waiting for may_assign */
> >> +  unsigned char   essential;      /* Is this task essential for the 
> >> system? */
> > AIUI only assign_active need to be adressable? Better make only that one
> > addressable.
> 
> Looking at the existing flag types, it needs to fit into part of a cacheline.

Why would it need to fit in a cacheline?

> The way I have done it, I rearranged the existing 4 byte integer to be 4 
> separate single byte flags.
> If you want me to put only one of the values into an addressable field,
> how will I retain the same size for the rest of the fields?

What do you mean by "the same size"?

Samuel