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Commit 557240b4 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

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: default avatarLinus Torvalds <torvalds@osdl.org>
parent 56035091

include/linux/console.h

+4 −0
Original line number Diff line number Diff line
@@ -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)

kernel/power/main.c

+2 −0
Original line number Diff line number Diff line
@@ -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)

kernel/printk.c

+27 −1
Original line number Diff line number Diff line
@@ -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;