linux-kernel - Re: [PATCH] mm: introduce arg_lock to protect arg_start|end and env_start|end in mm

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Message-ID: <20180326145505.GM5652@dhcp22.suse.cz>
Date:   Mon, 26 Mar 2018 16:55:05 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Yang Shi <yang.shi@...ux.alibaba.com>,
        Matthew Wilcox <willy@...radead.org>, adobriyan@...il.com,
        akpm@...ux-foundation.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: introduce arg_lock to protect arg_start|end and
 env_start|end in mm_struct

On Mon 26-03-18 23:49:18, Tetsuo Handa wrote:
[...]
> Also, even if we succeeded to avoid mmap_sem contention at that location,
> won't we after all get mmap_sem contention messages a bit later, for
> access_remote_vm() holds mmap_sem which would lead to traces like above
> if mmap_sem is already contended?

Yes, but at least we get rid of the mmap_sem for something that can use
a more fine grained locking.

Maybe we can get a finer grained range locking for mmap_sem one day and
not having the full range locked section will be a plus.

-- 
Michal Hocko
SUSE Labs