linux-kernel - Re: [PATCH 5/7] mm/page_alloc: Protect PCP lists with a spinlock

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] [day] [month] [year] [list]

Message-ID: <20220705072034.GC27531@techsingularity.net>
Date:   Tue, 5 Jul 2022 08:20:34 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Vlastimil Babka <vbabka@...e.cz>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Nicolas Saenz Julienne <nsaenzju@...hat.com>,
        Marcelo Tosatti <mtosatti@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Hugh Dickins <hughd@...gle.com>, Yu Zhao <yuzhao@...gle.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>
Subject: Re: [PATCH 5/7] mm/page_alloc: Protect PCP lists with a spinlock

On Mon, Jul 04, 2022 at 02:31:17PM +0200, Vlastimil Babka wrote:
> On 6/24/22 14:54, Mel Gorman wrote:
> > Currently the PCP lists are protected by using local_lock_irqsave to
> > prevent migration and IRQ reentrancy but this is inconvenient.  Remote
> > draining of the lists is impossible and a workqueue is required and every
> > task allocation/free must disable then enable interrupts which is
> > expensive.
> > 
> > As preparation for dealing with both of those problems, protect the lists
> > with a spinlock.  The IRQ-unsafe version of the lock is used because IRQs
> > are already disabled by local_lock_irqsave.  spin_trylock is used in
> > preparation for a time when local_lock could be used instead of
> > lock_lock_irqsave.
> 
>   ^ local_lock_irqsave?
> 

More appropriate given how the series evolved would be;

spin_trylock is used in combination with local_lock_irqsave() but later
will be replaced with a spin_trylock_irqsave when the local_lock is
removed.

-- 
Mel Gorman
SUSE Labs