linux-kernel - Re: [PATCH] prctl: Don't compile some of prctl functions when CRUI

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Date:   Wed, 17 Apr 2019 15:38:41 +0300
From:   Cyrill Gorcunov <gorcunov@...il.com>
To:     Michal Koutný <mkoutny@...e.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        kbuild-all@...org, LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...nel.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Andrey Vagin <avagin@...nvz.org>,
        Andrew Morton <akpm@...uxfoundation.org>,
        Pavel Emelyanov <xemul@...tuozzo.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        kbuild test robot <lkp@...el.com>
Subject: Re: [PATCH] prctl: Don't compile some of prctl functions when CRUI

On Wed, Apr 17, 2019 at 02:23:50PM +0200, Michal Koutný wrote:
> Hi.
> 
> I see this discussion somewhat faded away since the previous year.
> 
> There was rework [1] that reduced (ab)use of mmap_sem in prctl
> functions.
> 
> Actually, there still remains the down_write() in prctl_set_mm.
> I considered at least replacing it with the mm_struct.arg_lock +
> down_read() but then I learnt about this thread intending to remove that
> part completely. I wouldn't oppose if CRIU is the sole (aware) user.
> 
> Ad the bot build issue, I could build the kernel both with
> CONFIG_CHECKPOINT_RESTORE and without CONFIG_CHECKPOINT_RESTORE just
> fine after applying the two proposed patches.
> 
> What is the current state? Perhaps, this change should be CCed to
> linux-api@...r.kernel.org(?).
> 
> [1] https://lore.kernel.org/lkml/1523730291-109696-1-git-send-email-yang.shi@linux.alibaba.com/T/

Hi! I've a bit vague memory what we've ended up with, but iirc there was
a problem with brk() syscall or similar. Then I think we left everything
as is. I think there is no much activity in this prctl area now as far
as i know (replying to what is current state).