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@xxxxxxxxxxxxx>
---
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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