linux-kernel - [PATCH] Software Suspend: Fix suspend when console is in VT_AUTO+KD

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Date:	Mon, 12 Mar 2007 13:29:40 -0700
From:	Andrew Johnson <ajohnson@...rinsyc.com>
To:	linux-kernel@...r.kernel.org
Cc:	Pavel Machek <pavel@....cz>, akpm@...l.org
Subject: [PATCH] Software Suspend: Fix suspend when console is in
	VT_AUTO+KD_GRAPHICS mode

Hi All,

When the console is in VT_AUTO+KD_GRAPHICS mode, switching to the
SUSPEND_CONSOLE fails, resulting in vt_waitactive() waiting indefinitely
or until the task is interrupted.  This patch tests if a console switch
can occur in set_console() and returns early if a console switch is not
possible.

-- Andrew

Signed-off-by: Andrew Johnson <ajohnson@...rinsyc.com>
---
diff -rup linux-2.6.20.1/drivers/char/vt.c linux/drivers/char/vt.c
--- linux-2.6.20.1/drivers/char/vt.c	2007-02-19 22:34:32.000000000 -0800
+++ linux/drivers/char/vt.c	2007-03-12 12:37:44.000000000 -0700
@@ -2188,10 +2188,30 @@ static void console_callback(struct work
 	release_console_sem();
 }
 
-void set_console(int nr)
+extern char vt_dont_switch;
+
+int set_console(int nr)
 {
+	struct vc_data *vc = vc_cons[fg_console].d;
+
+	if (!vc_cons_allocated(nr) || vt_dont_switch || 
+		(vc->vt_mode.mode == VT_AUTO && vc->vc_mode == KD_GRAPHICS)) {
+
+		/* 
+		 * Console switch will fail in console_callback() or 
+		 * change_console() so there is no point scheduling 
+		 * the callback
+		 *
+		 * Existing set_console() users don't check the return
+		 * value so this shouldn't break anything 
+		 */ 
+		return -EINVAL;
+	}
+
 	want_console = nr;
 	schedule_console_callback();
+
+	return 0;
 }
 
 struct tty_driver *console_driver;
diff -rup linux-2.6.20.1/drivers/char/vt_ioctl.c linux/drivers/char/vt_ioctl.c
--- linux-2.6.20.1/drivers/char/vt_ioctl.c	2007-02-19 22:34:32.000000000 -0800
+++ linux/drivers/char/vt_ioctl.c	2007-03-08 14:15:41.000000000 -0800
@@ -34,7 +34,7 @@
 #include <linux/kbd_diacr.h>
 #include <linux/selection.h>
 
-static char vt_dont_switch;
+char vt_dont_switch;
 extern struct tty_driver *console_driver;
 
 #define VT_IS_IN_USE(i)	(console_driver->ttys[i] && console_driver->ttys[i]->count)
diff -rup linux-2.6.20.1/include/linux/kbd_kern.h linux/include/linux/kbd_kern.h
--- linux-2.6.20.1/include/linux/kbd_kern.h	2007-02-19 22:34:32.000000000 -0800
+++ linux/include/linux/kbd_kern.h	2007-03-08 14:15:41.000000000 -0800
@@ -75,7 +75,7 @@ extern int do_poke_blanked_console;
 
 extern void (*kbd_ledfunc)(unsigned int led);
 
-extern void set_console(int nr);
+extern int set_console(int nr);
 extern void schedule_console_callback(void);
 
 static inline void set_leds(void)
diff -rup linux-2.6.20.1/kernel/power/console.c linux/kernel/power/console.c
--- linux-2.6.20.1/kernel/power/console.c	2007-02-19 22:34:32.000000000 -0800
+++ linux/kernel/power/console.c	2007-03-09 15:52:32.000000000 -0800
@@ -27,7 +27,15 @@ int pm_prepare_console(void)
 		return 1;
 	}
 
-	set_console(SUSPEND_CONSOLE);
+	if (set_console(SUSPEND_CONSOLE)) {
+		/*
+		 * We're unable to switch to the SUSPEND_CONSOLE. 
+		 * Let the calling function know so it can decide 
+		 * what to do.
+		 */ 
+		release_console_sem();
+		return 1;
+	}
 	release_console_sem();
 
 	if (vt_waitactive(SUSPEND_CONSOLE)) {


-
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