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Date: Wed, 30 Jul 2008 00:18:34 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Ben Collins <ben.collins@...onical.com>
Cc: Greg KH <greg@...ah.com>, linux-kernel@...r.kernel.org,
Pavel Machek <pavel@....cz>,
pm list <linux-pm@...ts.linux-foundation.org>
Subject: Re: [PATCH 6/7] pm: Config option to disable handling of console during suspend/resume
On Tuesday, 29 of July 2008, Ben Collins wrote:
> On Tue, 2008-07-29 at 23:15 +0200, Rafael J. Wysocki wrote:
> > On Tuesday, 29 of July 2008, Greg KH wrote:
> > > On Sun, Jul 20, 2008 at 09:48:28PM -0400, Ben Collins wrote:
> > > > Config option allows userspace to handle console during suspend/resume
> > > > instead of the kernel.
> > > >
> > > > Signed-off-by: Ben Collins <ben.collins@...onical.com>
> > > > ---
> > > > kernel/power/Kconfig | 15 +++++++++++++++
> > > > kernel/power/console.c | 4 ++++
> > > > 2 files changed, 19 insertions(+), 0 deletions(-)
> > > >
> > > > diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> > > > index b45da40..6855299 100644
> > > > --- a/kernel/power/Kconfig
> > > > +++ b/kernel/power/Kconfig
> > > > @@ -105,6 +105,21 @@ config SUSPEND_FREEZER
> > > >
> > > > Turning OFF this setting is NOT recommended! If in doubt, say Y.
> > > >
> > > > +config PM_DISABLE_CONSOLE
> > > > + bool "Disable Power Management messing with the active console"
> > > > + depends on PM
> > > > + default n
> > > > + ---help---
> > > > + By default, PM will take over the active console (generally, this means
> > > > + switching to the console when suspending from X). This can at times cause
> > > > + problems, especially if userspace suspend scripts try to do things with
> > > > + the console before or after suspending (e.g. calling vbestate).
> > > > +
> > > > + To work around this, enable this option so that PM will not handle the
> > > > + console.
> > > > +
> > > > + If unsure, say N.
> > > > +
> > > > config HIBERNATION
> > > > bool "Hibernation (aka 'suspend to disk')"
> > > > depends on PM && SWAP && ARCH_HIBERNATION_POSSIBLE
> > > > diff --git a/kernel/power/console.c b/kernel/power/console.c
> > > > index b8628be..8b9706f 100644
> > > > --- a/kernel/power/console.c
> > > > +++ b/kernel/power/console.c
> > > > @@ -33,6 +33,7 @@ EXPORT_SYMBOL(pm_set_vt_switch);
> > > >
> > > > int pm_prepare_console(void)
> > > > {
> > > > +#ifndef CONFIG_PM_DISABLE_CONSOLE
> > >
> > > Can't you do this in a .h file instead?
> > >
> > > And is this really needed? Why has no other distro needed this change?
> > > What is so wierd about your suspend setup to require this?
> >
> > Reportedly, some systems have problems with graphics restoration from user
> > space if the switch is done.
> >
> > Anyway, I'd prefer to use the (already existing) pm_set_vt_switch() thing for
> > that, maybe with the help of a command line parameter, to adding the .config
> > option like this.
>
> Ah. I didn't notice pm_set_vt_switch(). Then what I would like better is
> the config option to set a default. For us, not doing the vt switch is a
> good default (I don't think we have a case where suspend/resume requires
> it).
As long as we freeze X, I don't think the switch is really necessary. I might
be wrong, though.
> Something like:
Well, why not.
[/me makes a note to change disable_vt_switch to 'bool' at some point in
future]
> diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
> index e7bea3e..6a042f8 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -2247,6 +2247,11 @@ and is between 256 and 4096 characters. It is defined in the file
> vmpoff= [KNL,S390] Perform z/VM CP command after power off.
> Format: <command>
>
> + vt_switch= [PM] Switch vt's during suspend/resume
> + Format: { 0 | 1 }
> + Default is normally '1', but depends on value of
> + the PM_DISABLE_CONSOLE config option.
> +
> waveartist= [HW,OSS]
> Format: <io>,<irq>,<dma>,<dma2>
>
> diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
> index dcd165f..202f9b3 100644
> --- a/kernel/power/Kconfig
> +++ b/kernel/power/Kconfig
> @@ -116,6 +116,25 @@ config SUSPEND_FREEZER
>
> Turning OFF this setting is NOT recommended! If in doubt, say Y.
>
> +config PM_DISABLE_CONSOLE
> + bool "Disable Power Management messing with the active console"
> + depends on PM
> + default n
> + ---help---
> + By default, PM will take over the active console (generally, this means
> + switching to the console when suspending from X). This can at times cause
> + problems, especially if userspace suspend scripts try to do things with
> + the console before or after suspending (e.g. calling vbestate).
> +
> + To work around this, enable this option so that PM will not handle the
> + console.
> +
> + Note, this is the same as passing vt_switch=0 command line option, but
> + just hardcodes the default. You can still pass vt_switch=1 with this
> + option to get original behavior.
> +
> + If unsure, say N.
> +
> config HIBERNATION
> bool "Hibernation (aka 'suspend to disk')"
> depends on PM && SWAP && ARCH_HIBERNATION_POSSIBLE
> diff --git a/kernel/power/console.c b/kernel/power/console.c
> index b8628be..db116d8 100644
> --- a/kernel/power/console.c
> +++ b/kernel/power/console.c
> @@ -14,7 +14,11 @@
> #define SUSPEND_CONSOLE (MAX_NR_CONSOLES-1)
>
> static int orig_fgconsole, orig_kmsg;
> +#ifdef CONFIG_PM_DISABLE_CONSOLE
> +static int disable_vt_switch = 1;
> +#else
> static int disable_vt_switch;
> +#endif
>
> /*
> * Normally during a suspend, we allocate a new console and switch to it.
> @@ -80,4 +84,17 @@ void pm_restore_console(void)
> release_console_sem();
> kmsg_redirect = orig_kmsg;
> }
> +
> +static int __init set_vt_switch(char *str)
> +{
> + if (str[0] == '0')
> + disable_vt_switch = 1;
> + else if (str[0] == '1')
> + disable_vt_switch = 0;
> + else
> + return -EINVAL;
> +
> + return 0;
> +}
> +__setup("vt_switch=", set_vt_switch);
> #endif
>
>
>
>
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