linux-kernel - Re: [PATCH 3/3] prctl_set_mm: downgrade mmap

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Message-ID: <20190430090808.GC2673@uranus.lan>
Date:   Tue, 30 Apr 2019 12:08:08 +0300
From:   Cyrill Gorcunov <gorcunov@...il.com>
To:     Kirill Tkhai <ktkhai@...tuozzo.com>
Cc:     Michal Koutný <mkoutny@...e.com>,
        akpm@...ux-foundation.org, arunks@...eaurora.org, brgl@...ev.pl,
        geert+renesas@...der.be, ldufour@...ux.ibm.com,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        mguzik@...hat.com, mhocko@...nel.org, rppt@...ux.ibm.com,
        vbabka@...e.cz
Subject: Re: [PATCH 3/3] prctl_set_mm: downgrade mmap_sem to read lock

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.