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Shutemov" , =?iso-8859-1?B?Suly9G1l?= Glisse , Andrea Arcangeli , David Rientjes , "Aneesh Kumar K.V" , swkhack , "Potyra, Stefan" , Mike Rapoport , Stephen Rothwell , Colin Ian King , Jason Gunthorpe , Mauro Carvalho Chehab , Peng Fan , Nikolay Borisov , Ira Weiny , Kirill Tkhai , Yafang Shao Subject: Re: [PATCH v4 3/9] mm/lru: replace pgdat lru_lock with lruvec lock Message-ID: <20191119164448.GA396644@cmpxchg.org> References: <1574166203-151975-1-git-send-email-alex.shi@linux.alibaba.com> <1574166203-151975-4-git-send-email-alex.shi@linux.alibaba.com> <20191119155704.GP20752@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191119155704.GP20752@bombadil.infradead.org> User-Agent: Mutt/1.12.2 (2019-09-21) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 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