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Message-Id: <1217368310.6066.56.camel@cunning>
Date: Tue, 29 Jul 2008 17:51:50 -0400
From: Ben Collins <ben.collins@...onical.com>
To: "Rafael J. Wysocki" <rjw@...k.pl>
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 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).
Something like:
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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