linux-kernel - Re: mm: use down_read_killable for locking mmap_sem in access_remote

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Message-ID: <20190515114954.GB31704@bombadil.infradead.org>
Date:   Wed, 15 May 2019 04:49:54 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Michal Koutný <mkoutny@...e.com>
Cc:     khlebnikov@...dex-team.ru, akpm@...ux-foundation.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org, oleg@...hat.com
Subject: Re: mm: use down_read_killable for locking mmap_sem in
 access_remote_vm

On Wed, May 15, 2019 at 10:38:26AM +0200, Michal Koutný wrote:
> Hi,
> making this holder of mmap_sem killable was for the reasons of /proc/...
> diagnostics was an idea I was pondeering too. However, I think the
> approach of pretending we read 0 bytes is not correct. The API would IMO
> need to be extended to allow pass a result such as EINTR to the end
> caller.
> Why do you think it's safe to return just 0?

_killable_, not _interruptible_.

The return value will never be seen by userspace because it's dead.