linux-kernel - Re: [PATCH] memcg: do not call reclaim if !__GFP

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]

Message-ID: <20150529065504.GA22728@dhcp22.suse.cz>
Date:	Fri, 29 May 2015 08:55:04 +0200
From:	Michal Hocko <mhocko@...e.cz>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Vladimir Davydov <vdavydov@...allels.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH] memcg: do not call reclaim if !__GFP_WAIT

On Thu 28-05-15 12:59:34, Andrew Morton wrote:
> On Thu, 28 May 2015 20:26:06 +0300 Vladimir Davydov <vdavydov@...allels.com> wrote:
> 
> > When trimming memcg consumption excess (see memory.high), we call
> > try_to_free_mem_cgroup_pages without checking if we are allowed to sleep
> > in the current context, which can result in a deadlock. Fix this.
> 
> Why does it deadlock?  try_to_free_mem_cgroup_pages() is passed the
> gfp_mask and should honour its __GFP_WAIT setting?

The only instance of __GFP_WAIT check in vmscan code is in zone_reclaim.
Page allocations and memcg reclaim avoids calling reclaim if __GFP_WAIT
is not set. Maybe we can move the check to do_try_to_free_pages?

-- 
Michal Hocko
SUSE Labs
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/