Fixes and cleanups for earlyprintk aka boot console

The console subsystem already has an idea of a boot console, using the
CON_BOOT flag.  The implementation has some flaws though.  The major
problem is that presence of a boot console makes register_console() ignore
any other console devices (unless explicitly specified on the kernel
command line).

This patch fixes the console selection code to *not* consider a boot
console a full-featured one, so the first non-boot console registering will
become the default console instead.  This way the unregister call for the
boot console in the register_console() function actually triggers and the
handover from the boot console to the real console device works smoothly.
Added a printk for the handover, so you know which console device the
output goes to when the boot console stops printing messages.

The disable_early_printk() call is obsolete with that patch, explicitly
disabling the early console isn't needed any more as it works automagically
with that patch.

I've walked through the tree, dropped all disable_early_printk() instances
found below arch/ and tagged the consoles with CON_BOOT if needed.  The
code is tested on x86, sh (thanks to Paul) and mips (thanks to Ralf).

Changes to last version: Rediffed against -rc3, adapted to mips cleanups by
Ralf, fixed "udbg-immortal" cmd line arg on powerpc.

Signed-off-by: Gerd Hoffmann <kraxel@exsuse.de>
Acked-by: Paul Mundt <lethal@linux-sh.org>
Acked-by: Ralf Baechle <ralf@linux-mips.org>
Cc: Andi Kleen <ak@suse.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

9 files changed, 35 insertions, 77 deletions

diff --git a/arch/alpha/kernel/setup.c b/arch/alpha/kernel/setup.c
index d352c2b05f1a..915f26345c45 100644
--- a/arch/alpha/kernel/setup.c
+++ b/arch/alpha/kernel/setup.c
@@ -744,15 +744,6 @@ setup_arch(char **cmdline_p)
         paging_init();
 }
 
-void __init
-disable_early_printk(void)
-{
-        if (alpha_using_srm && srmcons_output) {
-                unregister_srm_console();
-                srmcons_output = 0;
-        }
-}
-
 static char sys_unknown[] = "Unknown";
 static char systype_names[][16] = {
         "0",
diff --git a/arch/alpha/kernel/srmcons.c b/arch/alpha/kernel/srmcons.c
index 85a821aaceb4..930cedc8be24 100644
--- a/arch/alpha/kernel/srmcons.c
+++ b/arch/alpha/kernel/srmcons.c
@@ -300,7 +300,7 @@ static struct console srmcons = {
         .write          = srm_console_write,
         .device         = srm_console_device,
         .setup          = srm_console_setup,
-        .flags          = CON_PRINTBUFFER,
+        .flags          = CON_PRINTBUFFER | CON_BOOT,
         .index          = -1,
 };
 
diff --git a/arch/mips/kernel/early_printk.c b/arch/mips/kernel/early_printk.c
index 304efdc5682f..4fa54b230c09 100644
--- a/arch/mips/kernel/early_printk.c
+++ b/arch/mips/kernel/early_printk.c
@@ -33,8 +33,3 @@ void __init setup_early_printk(void)
 {
         register_console(&early_console);
 }
-
-void __init disable_early_printk(void)
-{
-        unregister_console(&early_console);
-}
diff --git a/arch/powerpc/kernel/udbg.c b/arch/powerpc/kernel/udbg.c
index 7e0971868fc2..147a2d83de10 100644
--- a/arch/powerpc/kernel/udbg.c
+++ b/arch/powerpc/kernel/udbg.c
@@ -142,29 +142,22 @@ static void udbg_console_write(struct console *con, const char *s,
 static struct console udbg_console = {
         .name   = "udbg",
         .write  = udbg_console_write,
-        .flags  = CON_PRINTBUFFER | CON_ENABLED,
+        .flags  = CON_PRINTBUFFER | CON_ENABLED | CON_BOOT,
         .index  = -1,
 };
 
 static int early_console_initialized;
 
-void __init disable_early_printk(void)
-{
-        if (!early_console_initialized)
-                return;
-        if (strstr(boot_command_line, "udbg-immortal")) {
-                printk(KERN_INFO "early console immortal !\n");
-                return;
-        }
-        unregister_console(&udbg_console);
-        early_console_initialized = 0;
-}
-
 /* called by setup_system */
 void register_early_udbg_console(void)
 {
         if (early_console_initialized)
                 return;
+
+        if (strstr(boot_command_line, "udbg-immortal")) {
+                printk(KERN_INFO "early console immortal !\n");
+                udbg_console.flags &= ~CON_BOOT;
+        }
         early_console_initialized = 1;
         register_console(&udbg_console);
 }
diff --git a/arch/sh/kernel/early_printk.c b/arch/sh/kernel/early_printk.c
index 9048c0326d87..9833493d8867 100644
--- a/arch/sh/kernel/early_printk.c
+++ b/arch/sh/kernel/early_printk.c
@@ -192,20 +192,14 @@ int __init setup_early_printk(char *buf)
         }
 #endif
 
-        if (likely(early_console))
+        if (likely(early_console)) {
+                if (keep_early)
+                        early_console->flags &= ~CON_BOOT;
+                else
+                        early_console->flags |= CON_BOOT;
                 register_console(early_console);
+        }
 
         return 0;
 }
 early_param("earlyprintk", setup_early_printk);
-
-void __init disable_early_printk(void)
-{
-        if (!early_console_initialized || !early_console)
-                return;
-        if (!keep_early) {
-                printk("disabling early console\n");
-                unregister_console(early_console);
-        } else
-                printk("keeping early console\n");
-}
diff --git a/arch/sh64/kernel/early_printk.c b/arch/sh64/kernel/early_printk.c
index 8c8a76e180aa..4f9131123672 100644
--- a/arch/sh64/kernel/early_printk.c
+++ b/arch/sh64/kernel/early_printk.c
@@ -79,7 +79,7 @@ static struct console sh_console = {
         .name           = "scifcon",
         .write          = sh_console_write,
         .setup          = sh_console_setup,
-        .flags          = CON_PRINTBUFFER,
+        .flags          = CON_PRINTBUFFER | CON_BOOT,
         .index          = -1,
 };
 
@@ -97,9 +97,3 @@ void __init enable_early_printk(void)
 
         register_console(&sh_console);
 }
-
-void disable_early_printk(void)
-{
-        unregister_console(&sh_console);
-}
-
diff --git a/arch/x86_64/kernel/early_printk.c b/arch/x86_64/kernel/early_printk.c
index 92213d2b7c11..56eaa259782b 100644
--- a/arch/x86_64/kernel/early_printk.c
+++ b/arch/x86_64/kernel/early_printk.c
@@ -243,22 +243,12 @@ static int __init setup_early_printk(char *buf)
                 early_console = &simnow_console;
                 keep_early = 1;
         }
+
+        if (keep_early)
+                early_console->flags &= ~CON_BOOT;
+        else
+                early_console->flags |= CON_BOOT;
         register_console(early_console);
         return 0;
 }
-
 early_param("earlyprintk", setup_early_printk);
-
-void __init disable_early_printk(void)
-{
-        if (!early_console_initialized || !early_console)
-                return;
-        if (!keep_early) {
-                printk("disabling early console\n");
-                unregister_console(early_console);
-                early_console_initialized = 0;
-        } else {
-                printk("keeping early console\n");
-        }
-}
-
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index 389da364e6b6..730cbd209a12 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -141,8 +141,6 @@ static DECLARE_MUTEX(allocated_ptys_lock);
 static int ptmx_open(struct inode *, struct file *);
 #endif
 
-extern void disable_early_printk(void);
-
 static void initialize_tty_struct(struct tty_struct *tty);
 
 static ssize_t tty_read(struct file *, char __user *, size_t, loff_t *);
@@ -3897,9 +3895,6 @@ void __init console_init(void)
          * set up the console device so that later boot sequences can 
          * inform about problems etc..
          */
-#ifdef CONFIG_EARLY_PRINTK
-        disable_early_printk();
-#endif
         call = __con_initcall_start;
         while (call < __con_initcall_end) {
                 (*call)();
diff --git a/kernel/printk.c b/kernel/printk.c
index 4b47e59248df..c4c5a29a7bed 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -931,8 +931,16 @@ void register_console(struct console *console)
 {
         int i;
         unsigned long flags;
+        struct console *bootconsole = NULL;
 
-        if (preferred_console < 0)
+        if (console_drivers) {
+                if (console->flags & CON_BOOT)
+                        return;
+                if (console_drivers->flags & CON_BOOT)
+                        bootconsole = console_drivers;
+        }
+
+        if (preferred_console < 0 || bootconsole || !console_drivers)
                 preferred_console = selected_console;
 
         /*
@@ -978,8 +986,11 @@ void register_console(struct console *console)
         if (!(console->flags & CON_ENABLED))
                 return;
 
-        if (console_drivers && (console_drivers->flags & CON_BOOT)) {
-                unregister_console(console_drivers);
+        if (bootconsole) {
+                printk(KERN_INFO "console handover: boot [%s%d] -> real [%s%d]\n",
+                       bootconsole->name, bootconsole->index,
+                       console->name, console->index);
+                unregister_console(bootconsole);
                 console->flags &= ~CON_PRINTBUFFER;
         }
 
@@ -1030,16 +1041,11 @@ int unregister_console(struct console *console)
                 }
         }
 
-        /* If last console is removed, we re-enable picking the first
-         * one that gets registered. Without that, pmac early boot console
-         * would prevent fbcon from taking over.
-         *
+        /*
          * If this isn't the last console and it has CON_CONSDEV set, we
          * need to set it on the next preferred console.
          */
-        if (console_drivers == NULL)
-                preferred_console = selected_console;
-        else if (console->flags & CON_CONSDEV)
+        if (console_drivers != NULL && console->flags & CON_CONSDEV)
                 console_drivers->flags |= CON_CONSDEV;
 
         release_console_sem();