From 557240b48e2dc4f6fa878afc3fc767ad745ca7ed Mon Sep 17 00:00:00 2001
From: Linus Torvalds <torvalds@g5.osdl.org>
Date: Mon, 19 Jun 2006 18:16:01 -0700
Subject: [PATCH] Add support for suspending and resuming the whole console
subsystem
Trying to suspend/resume with console messages flying all around is
doomed to failure, when the devices that the messages are trying to
go to are being shut down.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
---
include/linux/console.h | 4 ++++
kernel/power/main.c | 2 ++
kernel/printk.c | 28 +++++++++++++++++++++++++++-
3 files changed, 33 insertions(+), 1 deletion(-)
diff --git a/include/linux/console.h b/include/linux/console.h
index 721371382ae5..08734e660d41 100644
--- a/include/linux/console.h
+++ b/include/linux/console.h
@@ -117,6 +117,10 @@ extern void console_stop(struct console *);
extern void console_start(struct console *);
extern int is_console_locked(void);
+/* Suspend and resume console messages over PM events */
+extern void suspend_console(void);
+extern void resume_console(void);
+
/* Some debug stub to catch some of the obvious races in the VT code */
#if 1
#define WARN_CONSOLE_UNLOCKED() WARN_ON(!is_console_locked() && !oops_in_progress)
diff --git a/kernel/power/main.c b/kernel/power/main.c
index a6d9ef46009e..0a907f0dc56b 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -86,6 +86,7 @@ static int suspend_prepare(suspend_state_t state)
goto Thaw;
}
+ suspend_console();
if ((error = device_suspend(PMSG_SUSPEND))) {
printk(KERN_ERR "Some devices failed to suspend\n");
goto Finish;
@@ -133,6 +134,7 @@ int suspend_enter(suspend_state_t state)
static void suspend_finish(suspend_state_t state)
{
device_resume();
+ resume_console();
thaw_processes();
enable_nonboot_cpus();
if (pm_ops && pm_ops->finish)
diff --git a/kernel/printk.c b/kernel/printk.c
index c056f3324432..19a955619294 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -67,6 +67,7 @@ EXPORT_SYMBOL(oops_in_progress);
* driver system.
*/
static DECLARE_MUTEX(console_sem);
+static DECLARE_MUTEX(secondary_console_sem);
struct console *console_drivers;
/*
* This is used for debugging the mess that is the VT code by
@@ -76,7 +77,7 @@ struct console *console_drivers;
* path in the console code where we end up in places I want
* locked without the console sempahore held
*/
-static int console_locked;
+static int console_locked, console_suspended;
/*
* logbuf_lock protects log_buf, log_start, log_end, con_start and logged_chars
@@ -697,6 +698,23 @@ int __init add_preferred_console(char *name, int idx, char *options)
return 0;
}
+/**
+ * suspend_console - suspend the console subsystem
+ *
+ * This disables printk() while we go into suspend states
+ */
+void suspend_console(void)
+{
+ acquire_console_sem();
+ console_suspended = 1;
+}
+
+void resume_console(void)
+{
+ console_suspended = 0;
+ release_console_sem();
+}
+
/**
* acquire_console_sem - lock the console system for exclusive use.
*
@@ -708,6 +726,10 @@ int __init add_preferred_console(char *name, int idx, char *options)
void acquire_console_sem(void)
{
BUG_ON(in_interrupt());
+ if (console_suspended) {
+ down(&secondary_console_sem);
+ return;
+ }
down(&console_sem);
console_locked = 1;
console_may_schedule = 1;
@@ -750,6 +772,10 @@ void release_console_sem(void)
unsigned long _con_start, _log_end;
unsigned long wake_klogd = 0;
+ if (console_suspended) {
+ up(&secondary_console_sem);
+ return;
+ }
for ( ; ; ) {
spin_lock_irqsave(&logbuf_lock, flags);
wake_klogd |= log_start - log_end;
--
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