linux-kernel - Re: ftraced and suspend to ram

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Date:	Fri, 22 Aug 2008 23:17:56 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Marcin Slusarz <marcin.slusarz@...il.com>
Cc:	Pavel Machek <pavel@...e.cz>, Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Nigel Cunningham <nigel@...el.suspend2.net>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: ftraced and suspend to ram

On Friday, 22 of August 2008, Marcin Slusarz wrote:
> On Fri, Aug 22, 2008 at 06:39:34PM +0200, Rafael J. Wysocki wrote:
> > On Friday, 22 of August 2008, Marcin Slusarz wrote:
> > > On Fri, Aug 22, 2008 at 09:23:43AM +0200, Pavel Machek wrote:
> > > > > 
> > > > > * Rafael J. Wysocki <rjw@...k.pl> wrote:
> > > > > 
> > > > > > > > The code in question is the ftraced() function in 
> > > > > > > > kernel/trace/ftrace.c
> > > > > > > 
> > > > > > > Thanks, I'll have a look in a while.
> > > > > > 
> > > > > > Can you try the appended patch, please?
> > > > > 
> > > > > makes sense - i've applied it to tip/tracing/urgent, see the tidied up 
> > > > > commit below.
> > > > > 
> > > > > It should be no big issue not being able to trace across suspend+resume 
> > > > > - and that restriction will go away with Steve's build-time based mcount 
> > > > > patching mechanism in v2.6.28.
> > > > 
> > > > Patch looks okay to me, but I'm not sure if another issue is not
> > > > hiding under it. Did anyone actually test ftrace + suspend after
> > > > applying this?
> > > 
> > > I just tested this patch - it didn't help ;(
> > > 
> > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
> > > index 49f4c3f..02e41b2 100644
> > > --- a/kernel/trace/ftrace.c
> > > +++ b/kernel/trace/ftrace.c
> > > @@ -27,6 +27,7 @@
> > >  #include <linux/ctype.h>
> > >  #include <linux/hash.h>
> > >  #include <linux/list.h>
> > > +#include <linux/freezer.h>
> > >  
> > >  #include <asm/ftrace.h>
> > 
> > This is needed to fix compilation, sorry for the omission.
> > 
> > Still, did you test ftrace + suspend with the original patch and your fix
> > applied and if you did, then what happend?
> 
> Suspend works fine. When I hit power button I see some informations from
> video card (nvidia), then screen goes black and monitor says "no signal"
> and then I see the same informations from video card, then BIOS and GRUB.
> When everything works fine, X comes back after first infos from video card.

I suspect that something under arch/x86/kernel/acpi/realmode is broken
somehow.

Thanks,
Rafael
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