[RFC][PATCH 2/3] PM: Make console suspending configureable

Rafael J. Wysocki
2006-08-16T11:09:34Z

Change suspend_console() so that it waits for all consoles to flush the
remaining messages and make it possible to switch the console suspending
off with the help of a Kconfig option.

Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
---
include/linux/console.h | 5 +++++
kernel/power/Kconfig | 11 +++++++++++
kernel/printk.c | 8 ++++++++
3 files changed, 24 insertions(+)

Index: linux-2.6.18-rc4-mm1/include/linux/console.h
===================================================================
--- linux-2.6.18-rc4-mm1.orig/include/linux/console.h 2006-08-16 11:59:56.000000000 +0200
+++ linux-2.6.18-rc4-mm1/include/linux/console.h 2006-08-16 12:00:01.000000000 +0200
@@ -120,9 +120,14 @@ extern void console_stop(struct console
extern void console_start(struct console *);
extern int is_console_locked(void);

+#ifndef CONFIG_DISABLE_CONSOLE_SUSPEND
/* Suspend and resume console messages over PM events */
extern void suspend_console(void);
extern void resume_console(void);
+#else
+static inline void suspend_console(void) {}
+static inline void resume_console(void) {}
+#endif /* CONFIG_DISABLE_CONSOLE_SUSPEND */

/* Some debug stub to catch some of the obvious races in the VT code */
#if 1
Index: linux-2.6.18-rc4-mm1/kernel/power/Kconfig
===================================================================
--- linux-2.6.18-rc4-mm1.orig/kernel/power/Kconfig 2006-08-16 11:59:56.000000000 +0200
+++ linux-2.6.18-rc4-mm1/kernel/power/Kconfig 2006-08-16 12:01:26.000000000 +0200
@@ -36,6 +36,17 @@ config PM_DEBUG
code. This is helpful when debugging and reporting various PM bugs,
like suspend support.

+config PM_DISABLE_CONSOLE_SUSPEND
+ bool "Keep console(s) enabled during suspend/resume (DANGEROUS)"
+ depends on PM && PM_DEBUG
+ default n
+ ---help---
+ This option turns off the console suspend mechanism that prevents
+ debug messages from reaching the console during the suspend/resume
+ operations. This may be helpful when debugging device drivers'
+ suspend/resume routines, but may itself lead to problems, for example
+ if netconsole is used.
+
config PM_TRACE
bool "Suspend/resume event tracing"
depends on PM && PM_DEBUG && X86_32 && EXPERIMENTAL
Index: linux-2.6.18-rc4-mm1/kernel/printk.c
===================================================================
--- linux-2.6.18-rc4-mm1.orig/kernel/printk.c 2006-08-16 11:59:56.000000000 +0200
+++ linux-2.6.18-rc4-mm1/kernel/printk.c 2006-08-16 12:08:59.000000000 +0200
@@ -702,6 +702,7 @@ int __init add_preferred_console(char *n
return 0;
}

+#ifndef CONFIG_DISABLE_CONSOLE_SUSPEND
/**
* suspend_console - suspend the console subsystem
*
@@ -709,8 +710,14 @@ int __init add_preferred_console(char *n
*/
void suspend_console(void)
{
+ printk("Suspending console(s)\n");
acquire_console_sem();
console_suspended = 1;
+ /* This is needed so that all of the messages that have already been
+ * written to all consoles can be actually transmitted (eg. over a
+ * network) before we try to suspend the consoles' devices.
+ */
+ ssleep(2);
}

void resume_console(void)
@@ -718,6 +725,7 @@ void resume_console(void)
console_suspended = 0;
release_console_sem();
}
+#endif /* CONFIG_DISABLE_CONSOLE_SUSPEND */

/**
* acquire_console_sem - lock the console system for exclusive use.