lkml.org 
[lkml]   [2006]   [May]   [28]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] Longhaul - call suspend(PMSG_FREEZE) before and resume() after
Hi!

> I posted this to Dave Jones, but:
> > This really should also get posted to linux-kernel, though I don't
> > think people are going to be particularly enthusiastic about exposing
> > these innards to modules.
> So I'm posting this patch here too. I'm not subscribed to this list.
> If You wish email me.
> Minor change: preempt_disabled() goto_sleep_pci() and wakeup_pci()
> causes "sheduling while atomic". So in this patch below it isn't
> preempt_disabled(). But I think that this should be protected
> in some way.

Well, suspend/resume is normally called during system suspend/resume,
so it has 'interesting' locking requirements.

> How it works:
> 1. Call suspend(PMSG_FREEZE) for each block device.
> 2. Call suspend(PMSG_FREEZE) for each PCI device.
> 3. Change CPU frequency.
> 4. Call resume() for each PCI device.
> 5. Call resume() for each block device.
>
> Result: No more broken DMA transfers caused by frequency change.

Result: system hang if userspace tries to do request at the same time
-- PCI drivers probably were not designed for _that_... but we
probably want to fix them, anyway, so this is probably ok (but expect
to do some driver debugging).

But you should really add that preempt_disable and not try this on smp
system...
Pavel

--
Thanks for all the (sleeping) penguins.
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-05-28 09:19    [W:0.034 / U:13.548 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site