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Date: Fri, 23 Mar 2018 21:30:44 -0700
From: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH] mm: introduce arg_lock to protect arg_start|end and
 env_start|end in mm_struct
Message-ID: <20180324043044.GA22733@bombadil.infradead.org>
References: <1521851771-108673-1-git-send-email-yang.shi@linux.alibaba.com>
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To: Yang Shi <yang.shi@linux.alibaba.com>
Cc: adobriyan@gmail.com, mhocko@kernel.org, akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org

> So, introduce a new rwlock in mm_struct to protect the concurrent access
> to arg_start|end and env_start|end.

I don't think an rwlock makes much sense here.  There is almost no
concurrency on the read side, and an rwlock is more expensive than
a spinlock.  Just use a spinlock.