Hi Peter,
I walked through the reference counting, and it seems good to me
(though it did take a few passes to fully digest the invariants for
the fat cookie stuff).
> +unsigned long sched_core_alloc_cookie(unsigned int type)
> {
> struct sched_core_cookie *ck = kmalloc(sizeof(*ck), GFP_KERNEL);
> if (!ck)
> return 0;
> - refcount_set(&ck->refcnt, 1);
> + WARN_ON_ONCE(type > GROUP_COOKIE);
> + sched_core_init_cookie(ck, type);
> sched_core_get();
>
> - return (unsigned long)ck;
> + return (unsigned long)ck | type;
> }
This feels like it needs to be stronger than a WARN_ON_ONCE; could
create a corrupted address that we later try to kfree().
Also, for my own edification, why will the bottom two bits here always be 0?
> -unsigned long sched_core_alloc_cookie(void)
> +static inline void *cookie_ptr(unsigned long cookie)
> +{
> + return (void *)(cookie & ~3UL);
> +}
> +
> +static inline int cookie_type(unsigned long cookie)
> +{
> + return cookie & 3;
> +}
s/3/FAT_COOKIE
> +#define FAT_COOKIE 0x03
Move to sched.h to group with TASK/GROUP_COOKIE?
> +static unsigned long __sched_core_fat_cookie(struct task_struct *p,
> + void **spare_fat,
> + unsigned long cookie)
> +{
This function looks good to me, but could use some more comments about
the pre/post-condition assumptions. Ie. cookie already has a get()
associated with it, caller is expected to kfree the spare_fat.
> + raw_spin_lock_irqsave(&fat_lock, flags);
> + n = rb_find_add(&fat->node, &fat_root, fat_cmp);
> + raw_spin_unlock_irqrestore(&fat_lock, flags);
> +
> + if (n) {
> + sched_core_put_fat(fat);
> + fat = node_2_fat(n);
This put() doesn't seem strictly necessary; caller will be
unconditionally freeing the spare_fat. Keep anyway for completeness,
but add a comment?
