linux-kernel - Re: ftraced and suspend to ram

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Message-Id: <200808222252.12547.rjw@sisk.pl>
Date:	Fri, 22 Aug 2008 22:52:11 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Pavel Machek <pavel@...e.cz>,
	Marcin Slusarz <marcin.slusarz@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	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, Steven Rostedt wrote:
> 
> On Fri, 22 Aug 2008, Pavel Machek wrote:
> > 
> > Does ftrace hook itself onto _all_ the functions? Or all .c functions?
> 
> It hooks into all .c functions that are not annotated with "notrace"
> or the files have not been marked in the Makefile like:
> 
>   CFLAGS_REMOVE_<file>.o = -pg
> 
> 
> > 
> > I guess low-level suspend code needs to be exempt from
> > tracing. Certainly all the assembly functions.
> 
> I'm looking into that now too. Are the functions in arch/x86/power/cpu*.c 
> the suspend to ram code?

They contain code executed during suspend to RAM, but such code is also:
- in all files under arch/x86/kernel/acpi/
- in main.c, console.c under kernel/power
- in all files under drivers/acpi/sleep
- in drivers/acpi/hardware/hwsleep.c

Generally, ACPI is heavily involved and I'm not the right person to ask which
of the ACPI functions should get the 'notrace' thing.  Also, I'm not sure about
the device drivers' ->suspend() and ->resume() callbacks, especially for
sysdevs and ->suspend_late(), ->resume_early() for platform devices and PCI.

Well, how exactly suspend to RAM is broken by ftrace?

Rafael
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