From: Cyrill Gorcunov <gorcunov@gmail.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Hugh Dickins <hughd@google.com>,
Peter Feiner <pfeiner@google.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Pavel Emelyanov <xemul@parallels.com>,
Jamie Liu <jamieliu@google.com>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Andrew Morton <akpm@linux-foundation.org>,
Magnus Damm <magnus.damm@gmail.com>
Subject: Re: [PATCH v5] mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared
Date: Tue, 26 Aug 2014 18:19:14 +0400 [thread overview]
Message-ID: <20140826141914.GA8952@moon> (raw)
In-Reply-To: <20140826140419.GA10625@node.dhcp.inet.fi>
On Tue, Aug 26, 2014 at 05:04:19PM +0300, Kirill A. Shutemov wrote:
> > >
> > > But now I'm realizing that if this is the _only_ place which modifies
> > > vm_flags with down_read, then it's "probably" safe. I've a vague
> > > feeling that this was discussed before - is that so, Cyrill?
> >
> > Well, as far as I remember we were not talking before about vm_flags
> > and read-lock in this function, maybe it was on some unrelated lkml thread
> > without me CC'ed? Until I miss something obvious using read-lock here
> > for vm_flags modification should be safe, since the only thing which is
> > important (in context of vma-softdirty) is the vma's presence. Hugh,
> > mind to refresh my memory, how long ago the discussion took place?
>
> It seems safe in vma-softdirty context. But if somebody else will decide that
> it's fine to modify vm_flags without down_write (in their context), we
> will get trouble. Sasha will come with weird bug report one day ;)
>
> At least vm_flags must be updated atomically to avoid race in middle of
> load-modify-store.
Which race you mean here? Two concurrent clear-refs?
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next prev parent reply other threads:[~2014-08-26 14:19 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-20 21:46 [PATCH] mm: softdirty: write protect PTEs created for read faults after VM_SOFTDIRTY cleared Peter Feiner
2014-08-20 23:45 ` Kirill A. Shutemov
2014-08-21 19:37 ` Peter Feiner
2014-08-21 20:51 ` Cyrill Gorcunov
2014-08-21 21:39 ` Kirill A. Shutemov
2014-08-21 21:46 ` Peter Feiner
2014-08-21 21:51 ` Kirill A. Shutemov
2014-08-21 22:50 ` Peter Feiner
2014-08-22 6:33 ` Cyrill Gorcunov
2014-08-23 22:11 ` [PATCH v2 0/3] softdirty fix and write notification cleanup Peter Feiner
2014-08-23 22:11 ` [PATCH v2 1/3] mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared Peter Feiner
2014-08-23 23:00 ` Kirill A. Shutemov
2014-08-23 23:15 ` Peter Feiner
2014-08-23 23:50 ` Kirill A. Shutemov
2014-08-24 0:55 ` Peter Feiner
2014-08-23 22:12 ` [PATCH v2 2/3] mm: mprotect: preserve special page protection bits Peter Feiner
2014-08-23 22:12 ` [PATCH v2 3/3] mm: mmap: cleanup code that preserves special vm_page_prot bits Peter Feiner
2014-08-24 1:43 ` [PATCH v3] mm: softdirty: enable write notifications on VMAs after VM_SOFTDIRTY cleared Peter Feiner
2014-08-24 7:59 ` Kirill A. Shutemov
2014-08-24 19:22 ` Cyrill Gorcunov
2014-08-24 14:41 ` [PATCH v4] " Peter Feiner
2014-08-25 3:34 ` [PATCH v5] " Peter Feiner
2014-08-26 4:45 ` Hugh Dickins
2014-08-26 6:49 ` Cyrill Gorcunov
2014-08-26 14:04 ` Kirill A. Shutemov
2014-08-26 14:19 ` Cyrill Gorcunov [this message]
2014-08-26 14:56 ` Kirill A. Shutemov
2014-08-26 15:18 ` Cyrill Gorcunov
2014-08-26 15:43 ` Kirill A. Shutemov
2014-08-26 15:53 ` Cyrill Gorcunov
2014-08-27 23:12 ` Hugh Dickins
2014-08-28 6:31 ` Cyrill Gorcunov
2014-08-27 21:55 ` Hugh Dickins
2014-09-04 16:43 ` Peter Feiner
2014-09-07 21:31 ` Peter Feiner
2014-09-07 23:01 ` [PATCH v6] " Peter Feiner
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