lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Date:   Fri, 14 Aug 2020 17:08:02 +0800
From:   Chinwen Chang <>
To:     Michel Lespinasse <>
CC:     Matthias Brugger <>,
        Andrew Morton <>,
        Vlastimil Babka <>,
        "Daniel Jordan" <>,
        Davidlohr Bueso <>,
        Alexey Dobriyan <>,
        "Matthew Wilcox (Oracle)" <>,
        Jason Gunthorpe <>,
        Steven Price <>,
        Song Liu <>,
        Jimmy Assarsson <>,
        Huang Ying <>,
        LKML <>,
        <>, <>
Subject: Re: [PATCH v2 2/2] mm: proc: smaps_rollup: do not stall write
 attempts on mmap_lock

On Fri, 2020-08-14 at 01:35 -0700, Michel Lespinasse wrote:
> On Wed, Aug 12, 2020 at 7:13 PM Chinwen Chang
> <> wrote:
> > smaps_rollup will try to grab mmap_lock and go through the whole vma
> > list until it finishes the iterating. When encountering large processes,
> > the mmap_lock will be held for a longer time, which may block other
> > write requests like mmap and munmap from progressing smoothly.
> >
> > There are upcoming mmap_lock optimizations like range-based locks, but
> > the lock applied to smaps_rollup would be the coarse type, which doesn't
> > avoid the occurrence of unpleasant contention.
> >
> > To solve aforementioned issue, we add a check which detects whether
> > anyone wants to grab mmap_lock for write attempts.
> I think your retry mechanism still doesn't handle all cases. When you
> get back the mmap lock, the address where you stopped last time could
> now be in the middle of a vma. I think the consistent thing to do in
> that case would be to retry scanning from the address you stopped at,
> even if it's not on a vma boundary anymore. You may have to change
> smap_gather_stats to support that, though.

Hi Michel,

I think I got your point. Let me try to prepare new patch series for
further reviews.

Thank you for your suggestion :)


Powered by blists - more mailing lists