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>

3 files changed, 33 insertions, 1 deletions

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
@@ -698,6 +699,23 @@ int __init add_preferred_console(char *name, int idx, char *options)
 }
 
 /**
+ * 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.
  *
  * Acquires a semaphore which guarantees that the caller has
@@ -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;