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Date:   Tue, 30 Apr 2019 12:08:08 +0300
From:   Cyrill Gorcunov <gorcunov@gmail.com>
To:     Kirill Tkhai <ktkhai@virtuozzo.com>
Cc:     Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny@suse.com>,
        akpm@linux-foundation.org, arunks@codeaurora.org, brgl@bgdev.pl,
        geert+renesas@glider.be, ldufour@linux.ibm.com,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org,
        mguzik@redhat.com, mhocko@kernel.org, rppt@linux.ibm.com,
        vbabka@suse.cz
Subject: Re: [PATCH 3/3] prctl_set_mm: downgrade mmap_sem to read lock
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On Tue, Apr 30, 2019 at 11:55:45AM +0300, Kirill Tkhai wrote:
> > -	up_write(&mm->mmap_sem);
> > +	spin_unlock(&mm->arg_lock);
> > +	up_read(&mm->mmap_sem);
> >  	return error;
> 
> Hm, shouldn't spin_lock()/spin_unlock() pair go as a fixup to existing code
> in a separate patch? 
> 
> Without them, the existing code has a problem at least in get_mm_cmdline().

Seems reasonable to merge it into patch 1.