Messages in this thread | | | Subject | Re: [PATCH v2] jump_label: reduce the size of struct static_key | From | Jason Baron <> | Date | Fri, 20 Jan 2017 15:02:01 -0500 |
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On 01/20/2017 02:19 AM, Ingo Molnar wrote: > > * Jason Baron <jbaron@akamai.com> wrote: > >> struct static_key { >> atomic_t enabled; >> +/* >> + * bit 0 => 1 if key is initially true >> + * 0 if initially false >> + * bit 1 => 1 if points to struct static_key_mod >> + * 0 if points to struct jump_entry >> + */ >> + union { >> + unsigned long type; >> + struct jump_entry *entries; >> + struct static_key_mod *next; >> + }; > > >> + key->type = (unsigned long)jlm2 | static_key_type(key); > >> + key->type = (unsigned long)jlm | static_key_type(key); > >> + *prev = (struct static_key_mod *)((unsigned long)jlm->next | >> + ((unsigned long)*prev & JUMP_TYPE_MASK)); > >> + key->type = (unsigned long)jlm->entries | >> + static_key_type(key); > > I really hate these very ugly type conversions. Is there no cleaner way? > > For example the last line could sure be written as: > > key->entries = jlm->entries; > key->type |= static_key_type(key); > > right?
Hi,
So that is going to over-write the static_key_type(key) in the first assignment. If the order is reversed we can't just |= in the pointer type.
How about:
static void jump_key_set_entries(struct static_key *key, struct jump_entry *entries) { unsigned long type;
type = static_key_type(key); key->entries = entries; key->type |= type; }
and then we can also add:
void jump_key_set_mod(struct static_key *key, struct static_key_mod *mod)
doing basically the same thing. That will avoid the casts that you called out.
better?
Thanks,
-Jason
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