在 2019/11/20 上午12:44, Johannes Weiner 写道:
> On Tue, Nov 19, 2019 at 07:57:04AM -0800, Matthew Wilcox wrote:
>> On Tue, Nov 19, 2019 at 08:23:17PM +0800, Alex Shi wrote:
>>> +static inline struct lruvec *lock_page_lruvec_irqsave(struct page *page,
>>> + struct pglist_data *pgdat, unsigned long *flags)
>>> +{
>>> + struct lruvec *lruvec = mem_cgroup_page_lruvec(page, pgdat);
>>> +
>>> + spin_lock_irqsave(&lruvec->lru_lock, *flags);
>>> +
>>> + return lruvec;
>>> +}
>>
>> This should be a macro, not a function. You basically can't do this;
>> spin_lock_irqsave needs to write to a variable which can then be passed
>> to spin_unlock_irqrestore(). What you're doing here will dereference the
>> pointer in _this_ function, but won't propagate the modified value back to
>> the caller. I suppose you could do something like this ...
>
> This works because spin_lock_irqsave and local_irq_save() are
> macros. It boils down to '*flags = arch_local_irq_save()' in this
> function, and therefor does the right thing.
>
> We exploit that in quite a few places:
>
> $ git grep 'spin_lock_irqsave(.*\*flags' | wc -l
> 39
>
Yes, thank you all for point this!
