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  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:   Tue, 15 Dec 2020 13:38:02 +0100
From:   Johannes Weiner <>
To:     Yang Shi <>
Subject: Re: [v2 PATCH 3/9] mm: vmscan: guarantee shrinker_slab_memcg() sees
 valid shrinker_maps for online memcg

On Mon, Dec 14, 2020 at 02:37:16PM -0800, Yang Shi wrote:
> The shrink_slab_memcg() races with mem_cgroup_css_online(). A visibility of CSS_ONLINE flag
> in shrink_slab_memcg()->mem_cgroup_online() does not guarantee that we will see
> memcg->nodeinfo[nid]->shrinker_maps != NULL.  This may occur because of processor reordering
> on !x86.
> This seems like the below case:
>            CPU A          CPU B
> store shrinker_map      load CSS_ONLINE
> store CSS_ONLINE        load shrinker_map
> So the memory ordering could be guaranteed by smp_wmb()/smp_rmb() pair.
> The memory barriers pair will guarantee the ordering between shrinker_deferred and CSS_ONLINE
> for the following patches as well.
> Signed-off-by: Yang Shi <>

As per previous feedback, please move the misplaced shrinker
allocation callback from .css_online to .css_alloc. This will get you
the necessary ordering guarantees from the cgroup core code.


Powered by blists - more mailing lists