From: matthieu.castet@parrot•com (Matthieu CASTET)
To: linux-arm-kernel@lists•infradead.org
Subject: [RFC PATCH v5] ARM hibernation / suspend-to-disk (fwd)
Date: Tue, 5 Jul 2011 19:09:19 +0200 [thread overview]
Message-ID: <4E13453F.1000009@parrot.com> (raw)
In-Reply-To: <2C577202CB5719438D4E9608C565CB2C01B69D7F@NL-EXC-07.intra.local>
Frank Hofmann a ?crit :
> -----Original Message-----
> From: Matthieu CASTET [mailto:matthieu.castet at parrot.com]
> Frank Hofmann a ?crit :
>> [ ... ]
>> > +static void notrace __swsusp_arch_restore_image(void)
>> > +{
>> > + extern struct pbe *restore_pblist;
>> > + struct pbe *pbe;
>> > +
>> > + cpu_switch_mm(swapper_pg_dir, &init_mm);
>> > +
>> > + for (pbe = restore_pblist; pbe; pbe = pbe->next)
>> > + copy_page(pbe->orig_address, pbe->address);
>> > +
>>
>> One question : isn't dangerous to modify the code where we are running ?
>>
>> I believe the code shouldn't change too much between the kernel that
> do the
>> resume and the resumed kernel and the copy routine should fit in the
> instruction
>> cache, but I want to be sure it doesn't cause any problem on recent
> arm cores
>> (instruction prefetching , ...)
>>
>>
>> Matthieu
>
> Hi Matthieu,
>
> this isn't new behaviour to _this_ rev of the patch ...
yes
>
> and yes, it is dangerous to modify code where you're running. Except
> that this isn't happening in the current environment;
You are modifying it by putting the same code (modulo dynamic patching on the
code (ftrace, kprobe, ...)).
> If you're resuming via some other
> mechanism but the kernel's snapshot image loading code (and only jump
> into swsusp_arch_resume to kickstart resume) then it's up to you how you
> get the kernel text into place.
Yes.
> I've not experimented with resuming "foreign" images; how would one
> create such, and bypass the checks on load ?
I wasn't suggesting that.
>
> It's less of a problem for the copy loop itself, really, as that's
> definitely cache-hot. But it's an issue for what happens _after_ the
> copy loop. If the code for cpu_resume / cpu_reset is not at the places
> where the resum-ing code expects it to be (i.e. if there's a mismatch in
> the resuming and to-be-resumed kernels wrt. to that), then things will
> jump to code nirvana.
>
> Why are you asking about this ?
While reading the code I was surprised of that. And that there weren't any
comment about it.
Looking at other implementations, only x86_64 seems to need to relocate the copy
code.
Matthieu
next prev parent reply other threads:[~2011-07-05 17:09 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-13 12:04 [RFC PATCH v5] ARM hibernation / suspend-to-disk (fwd) Frank Hofmann
2011-06-13 12:26 ` Russell King - ARM Linux
2011-06-13 12:40 ` Frank Hofmann
2011-06-13 13:20 ` Frank Hofmann
2011-06-13 13:56 ` Dave Martin
2011-06-13 15:34 ` Frank Hofmann
2011-06-13 16:11 ` Frank Hofmann
2011-06-13 16:44 ` Russell King - ARM Linux
2011-06-15 13:35 ` Frank Hofmann
2011-06-16 21:31 ` Russell King - ARM Linux
2011-06-20 12:32 ` Frank Hofmann
2011-06-21 14:35 ` Russell King - ARM Linux
2011-06-29 14:52 ` Matthieu CASTET
2011-06-29 15:14 ` Frank Hofmann
2011-06-29 20:08 ` Will Deacon
2011-07-05 12:37 ` Matthieu CASTET
[not found] ` <2C577202CB5719438D4E9608C565CB2C01B69D7F@NL-EXC-07.intra.local>
2011-07-05 17:09 ` Matthieu CASTET [this message]
2011-09-30 7:48 ` Barry Song
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