linux-kernel - Re: [PATCH v2 1/1] mm: initialize pages on demand during boot

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 8 Feb 2018 19:58:28 -0500
From:   Pavel Tatashin <pasha.tatashin@...cle.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     Steve Sistare <steven.sistare@...cle.com>,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        m.mizuma@...fujitsu.com, Michal Hocko <mhocko@...e.com>,
        Catalin Marinas <catalin.marinas@....com>,
        AKASHI Takahiro <takahiro.akashi@...aro.org>,
        Gioh Kim <gi-oh.kim@...fitbricks.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        baiyaowei@...s.chinamobile.com,
        Wei Yang <richard.weiyang@...il.com>,
        Paul Burton <paul.burton@...s.com>,
        Miles Chen <miles.chen@...iatek.com>,
        Vlastimil Babka <vbabka@...e.cz>, Mel Gorman <mgorman@...e.de>,
        Johannes Weiner <hannes@...xchg.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: [PATCH v2 1/1] mm: initialize pages on demand during boot

>>
>> It would be nice to have a little comment explaining why READ_ONCE was
>> needed.
>>
>> Would it still be needed if this code was moved into the locked region?
>
>
> No, we would need to use READ_ONCE() if we grabbed deferred_zone_grow_lock
> before this code. In fact I do not even think we strictly need READ_ONCE()
> here, as it is a single load anyway. But, because we are outside of the
> lock, and we want to quickly fetch the data with a single load, I think it
> makes sense to emphasize it using READ_ONCE() without expected compiler to
> simply do the write thing for us.
>
>

Correction:

No, we would NOT need ...