From: SeongJae Park <sj@kernel.org>
To: Matthew Wilcox <willy@infradead.org>
Cc: SeongJae Park <sj@kernel.org>,
akpm@linux-foundation.org, alexander.h.duyck@linux.intel.com,
paulmck@kernel.org, linux-mm@kvack.org, rcu@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/page_reporting: replace rcu_access_pointer() with rcu_dereference_protected()
Date: Tue, 27 Dec 2022 19:56:59 +0000 [thread overview]
Message-ID: <20221227195659.2876-1-sj@kernel.org> (raw)
In-Reply-To: <Y6tNnQvGGV+JVgC7@casper.infradead.org>
On Tue, 27 Dec 2022 19:55:09 +0000 Matthew Wilcox <willy@infradead.org> wrote:
> On Tue, Dec 27, 2022 at 07:21:58PM +0000, SeongJae Park wrote:
> > +++ b/mm/page_reporting.c
> > @@ -356,7 +356,7 @@ int page_reporting_register(struct page_reporting_dev_info *prdev)
> > mutex_lock(&page_reporting_mutex);
> >
> > /* nothing to do if already in use */
> > - if (rcu_access_pointer(pr_dev_info)) {
> > + if (rcu_dereference_protected(pr_dev_info, true)) {
>
> Pretty sure that passing a bare 'true' is an antipattern.
> Instead, document _what_ lock protects us, ie:
>
> if (rcu_dereference_protected(pr_dev_info,
> lockdep_is_held(&page_reporting_mutex))) {
>
> Obviously, we took it just one line up, but if code moves around, it
> may save us.
Good point, agreed. Will do so in the next version.
Thanks,
SJ
prev parent reply other threads:[~2022-12-27 19:57 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-12-27 19:21 [PATCH] mm/page_reporting: replace rcu_access_pointer() with rcu_dereference_protected() SeongJae Park
2022-12-27 19:55 ` Matthew Wilcox
2022-12-27 19:56 ` SeongJae Park [this message]
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