From: "Rafael J. Wysocki" <rjw@sisk.pl>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: Pavel Machek <pavel@ucw.cz>,
Goswin von Brederlow <goswin-v-b@web.de>,
Li Fei <fei.li@intel.com>,
len.brown@intel.com, mingo@redhat.com, peterz@infradead.org,
biao.wang@intel.com, linux-pm@vger.kernel.org,
fuse-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org,
chuansheng.liu@intel.com
Subject: Re: Getting rid of freezer for suspend [was Re: [fuse-devel] [PATCH] fuse: make fuse daemon frozen along with kernel threads]
Date: Wed, 13 Feb 2013 22:21:11 +0100 [thread overview]
Message-ID: <24327774.p6haZy6gvA@vostro.rjw.lan> (raw)
In-Reply-To: <CAJfpegsFThkzv3uF60AMXO7Y-yEzU_20HeGyPra0O8Vk5OqCGQ@mail.gmail.com>
On Wednesday, February 13, 2013 06:34:16 PM Miklos Szeredi wrote:
> On Tue, Feb 12, 2013 at 2:17 PM, Miklos Szeredi <miklos@szeredi.hu> wrote:
> > On Tue, Feb 12, 2013 at 2:13 PM, Miklos Szeredi <miklos@szeredi.hu> wrote:
> >> On Tue, Feb 12, 2013 at 11:46 AM, Pavel Machek <pavel@ucw.cz> wrote:
> >>
> >>> (After all, with FUSE, filesystem clients are just doing IPC. In ideal
> >>> world, that would be freezeable and killable with -9).
>
> Well, I thought this can be constrained to locks directly related to
> the fuse filesystem itself, but it can't... The reason is page
> faults. Pretty much everyone and their brother uses get_user_pages*,
> holding various locks (mmap_sem for sure but others as well). A fuse
> filesystem frozen during a page read will block those.
>
> Separating those parts of the kernel that can be frozen from those
> that can't looks increasingly difficult.
>
> So I think the PF_FREEZE_DAEMON idea (the patch from Li Fei that
> started this thread) may still be our best bet at handling this
> situation. The idea being that pure "originator" processes (ones that
> take no part in serving filesystem syscalls) can be frozen up-front.
> Then the "fuse daemon" (or "server") processes are hopefully in a
> quiescent state and can be frozen without difficulty.
>
> Unfortunately it needs help from userspace: the kernel can't easily
> guess which processes are part of a "fuse daemon" and which aren't.
> Fortunately we have a standard library (libfuse) that can tell it to
> the kernel for the vast majority of cases.
So basically the idea would be to introduce something like PF_FREEZE_LATE
for user space processes that need to be frozen after all of the other
(non-PF_FREEZE_LATE) user space processes have been frozen and hack fuse
to use that flag?
Rafael
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
next prev parent reply other threads:[~2013-02-13 21:14 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-06 1:11 [PATCH] fuse: make fuse daemon frozen along with kernel threads Li Fei
2013-02-06 9:27 ` Miklos Szeredi
[not found] ` <20130207084144.GB6168@frosties>
2013-02-07 9:59 ` [fuse-devel] " Miklos Szeredi
2013-02-08 14:11 ` Goswin von Brederlow
2013-02-09 17:49 ` Pavel Machek
2013-02-09 20:31 ` Rafael J. Wysocki
2013-02-10 10:33 ` Getting rid of freezer for suspend [was Re: [fuse-devel] [PATCH] fuse: make fuse daemon frozen along with kernel threads] Pavel Machek
2013-02-10 13:51 ` Rafael J. Wysocki
2013-02-10 14:22 ` Rafael J. Wysocki
2013-02-10 18:55 ` Pavel Machek
2013-02-10 23:31 ` Rafael J. Wysocki
2013-02-11 10:11 ` Miklos Szeredi
2013-02-11 12:08 ` Rafael J. Wysocki
2013-02-11 13:59 ` Miklos Szeredi
2013-02-11 19:28 ` Rafael J. Wysocki
2013-02-12 10:46 ` Pavel Machek
2013-02-12 13:13 ` Miklos Szeredi
2013-02-12 13:17 ` Miklos Szeredi
2013-02-13 17:34 ` Miklos Szeredi
2013-02-13 20:16 ` Pavel Machek
2013-02-14 10:31 ` Miklos Szeredi
2013-02-13 21:21 ` Rafael J. Wysocki [this message]
2013-02-14 10:41 ` Miklos Szeredi
2013-02-14 12:11 ` Rafael J. Wysocki
2013-02-14 13:09 ` Miklos Szeredi
2013-02-14 17:38 ` Rafael J. Wysocki
2013-02-18 6:26 ` Li, Fei
2013-02-18 12:26 ` Rafael J. Wysocki
2013-02-19 10:46 ` Pavel Machek
2013-02-20 2:54 ` Li, Fei
2013-02-20 13:13 ` [fuse-devel] Getting rid of freezer for suspend [was " Miklos Szeredi
2013-02-11 10:53 ` Getting rid of freezer for suspend [was Re: [fuse-devel] " Pavel Machek
2013-02-06 9:56 ` [fuse-devel] [PATCH] fuse: make fuse daemon frozen along with kernel threads Han-Wen Nienhuys
2013-02-06 14:59 ` Miklos Szeredi
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