linux-kernel - Re: mlockall(MCL_CURRENT) blocking infinitely

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Message-ID: <f4b9eac618c444092dc1154597d228f348122b38.camel@gmx.de>
Date:   Wed, 06 Nov 2019 13:24:58 +0100
From:   Robert Stupp <snazy@....de>
To:     snazy@...zy.de, Johannes Weiner <hannes@...xchg.org>,
        Vlastimil Babka <vbabka@...e.cz>
Cc:     Michal Hocko <mhocko@...nel.org>,
        Josef Bacik <josef@...icpanda.com>, Jan Kara <jack@...e.cz>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Randy Dunlap <rdunlap@...radead.org>,
        linux-kernel@...r.kernel.org, Linux MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Potyra, Stefan" <Stefan.Potyra@...ktrobit.com>
Subject: Re: mlockall(MCL_CURRENT) blocking infinitely

Oh! That (s/__get_user_pages()/__get_user_pages_locked()/) seems to fix
it.

Attached a patch (gup-mlockall.txt, against v5.3.8) - although, I've
got no clue how patches work here.
gup-debug-mlockall.txt is the debug printk() I've added plus the code
change.
dmesg-out.txt.gz is the dmesg output of the latter for test.c


On Wed, 2019-11-06 at 12:26 +0100, Robert Stupp wrote:
> Maybe a native and wrong idea, but would it work to call
> __get_user_pages_locked() instead of __get_user_pages() in
> populate_vma_page_range() ?
>
> On Wed, 2019-11-06 at 11:25 +0100, Robert Stupp wrote:
> > Here's one more dmesg output with more information captured in
> > __get_user_pages() as well. It basically confirms that
> > handle_mm_fault() returns VM_FAULT_RETRY.
> >
> > I'm not sure where and what to change ("fix with a FOLL_TRIED
> > somewhere") to make it work. My (uneducated) impression is, that
> > only
> > __get_user_pages() needs to be changed - but I might be wrong.
> >


View attachment "gup-mlockall.txt" of type "text/plain" (2313 bytes)

View attachment "gup-debug-mlockall.txt" of type "text/plain" (15994 bytes)

Download attachment "dmesg-out.txt.gz" of type "application/gzip" (17577 bytes)

View attachment "test.c" of type "text/x-csrc" (319 bytes)