1 files changed, 118 insertions, 57 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index b4d97b54c1ec..e10d193a833a 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -37,6 +37,12 @@
 #include <asm/uaccess.h>
 
 /*
+ * for_each_console() allows you to iterate on each console
+ */
+#define for_each_console(con) \
+        for (con = console_drivers; con != NULL; con = con->next)
+
+/*
  * Architectures can override it:
  */
 void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
@@ -61,6 +67,8 @@ int console_printk[4] = {
         DEFAULT_CONSOLE_LOGLEVEL,       /* default_console_loglevel */
 };
 
+static int saved_console_loglevel = -1;
+
 /*
  * Low level drivers may need that to know if they can schedule in
  * their unblank() callback or not. So let's export it.
@@ -372,10 +380,15 @@ int do_syslog(int type, char __user *buf, int len)
                 logged_chars = 0;
                 break;
         case 6:         /* Disable logging to console */
+                if (saved_console_loglevel == -1)
+                        saved_console_loglevel = console_loglevel;
                 console_loglevel = minimum_console_loglevel;
                 break;
         case 7:         /* Enable logging to console */
-                console_loglevel = default_console_loglevel;
+                if (saved_console_loglevel != -1) {
+                        console_loglevel = saved_console_loglevel;
+                        saved_console_loglevel = -1;
+                }
                 break;
         case 8:         /* Set level of messages printed to console */
                 error = -EINVAL;
@@ -384,6 +397,8 @@ int do_syslog(int type, char __user *buf, int len)
                 if (len < minimum_console_loglevel)
                         len = minimum_console_loglevel;
                 console_loglevel = len;
+                /* Implicitly re-enable logging to console */
+                saved_console_loglevel = -1;
                 error = 0;
                 break;
         case 9:         /* Number of chars in the log buffer */
@@ -412,7 +427,7 @@ static void __call_console_drivers(unsigned start, unsigned end)
 {
         struct console *con;
 
-        for (con = console_drivers; con; con = con->next) {
+        for_each_console(con) {
                 if ((con->flags & CON_ENABLED) && con->write &&
                                 (cpu_online(smp_processor_id()) ||
                                 (con->flags & CON_ANYTIME)))
@@ -544,7 +559,7 @@ static int have_callable_console(void)
 {
         struct console *con;
 
-        for (con = console_drivers; con; con = con->next)
+        for_each_console(con)
                 if (con->flags & CON_ANYTIME)
                         return 1;
 
@@ -1082,7 +1097,7 @@ void console_unblank(void)
 
         console_locked = 1;
         console_may_schedule = 0;
-        for (c = console_drivers; c != NULL; c = c->next)
+        for_each_console(c)
                 if ((c->flags & CON_ENABLED) && c->unblank)
                         c->unblank();
         release_console_sem();
@@ -1097,7 +1112,7 @@ struct tty_driver *console_device(int *index)
         struct tty_driver *driver = NULL;
 
         acquire_console_sem();
-        for (c = console_drivers; c != NULL; c = c->next) {
+        for_each_console(c) {
                 if (!c->device)
                         continue;
                 driver = c->device(c, index);
@@ -1134,25 +1149,49 @@ EXPORT_SYMBOL(console_start);
  * to register the console printing procedure with printk() and to
  * print any messages that were printed by the kernel before the
  * console driver was initialized.
+ *
+ * This can happen pretty early during the boot process (because of
+ * early_printk) - sometimes before setup_arch() completes - be careful
+ * of what kernel features are used - they may not be initialised yet.
+ *
+ * There are two types of consoles - bootconsoles (early_printk) and
+ * "real" consoles (everything which is not a bootconsole) which are
+ * handled differently.
+ *  - Any number of bootconsoles can be registered at any time.
+ *  - As soon as a "real" console is registered, all bootconsoles
+ *    will be unregistered automatically.
+ *  - Once a "real" console is registered, any attempt to register a
+ *    bootconsoles will be rejected
  */
-void register_console(struct console *console)
+void register_console(struct console *newcon)
 {
         int i;
         unsigned long flags;
-        struct console *bootconsole = NULL;
+        struct console *bcon = NULL;
 
-        if (console_drivers) {
-                if (console->flags & CON_BOOT)
-                        return;
-                if (console_drivers->flags & CON_BOOT)
-                        bootconsole = console_drivers;
+        /*
+         * before we register a new CON_BOOT console, make sure we don't
+         * already have a valid console
+         */
+        if (console_drivers && newcon->flags & CON_BOOT) {
+                /* find the last or real console */
+                for_each_console(bcon) {
+                        if (!(bcon->flags & CON_BOOT)) {
+                                printk(KERN_INFO "Too late to register bootconsole %s%d\n",
+                                        newcon->name, newcon->index);
+                                return;
+                        }
+                }
         }
 
-        if (preferred_console < 0 || bootconsole || !console_drivers)
+        if (console_drivers && console_drivers->flags & CON_BOOT)
+                bcon = console_drivers;
+
+        if (preferred_console < 0 || bcon || !console_drivers)
                 preferred_console = selected_console;
 
-        if (console->early_setup)
-                console->early_setup();
+        if (newcon->early_setup)
+                newcon->early_setup();
 
         /*
          *      See if we want to use this console driver. If we
@@ -1160,13 +1199,13 @@ void register_console(struct console *console)
          *      that registers here.
          */
         if (preferred_console < 0) {
-                if (console->index < 0)
-                        console->index = 0;
-                if (console->setup == NULL ||
-                    console->setup(console, NULL) == 0) {
-                        console->flags |= CON_ENABLED;
-                        if (console->device) {
-                                console->flags |= CON_CONSDEV;
+                if (newcon->index < 0)
+                        newcon->index = 0;
+                if (newcon->setup == NULL ||
+                    newcon->setup(newcon, NULL) == 0) {
+                        newcon->flags |= CON_ENABLED;
+                        if (newcon->device) {
+                                newcon->flags |= CON_CONSDEV;
                                 preferred_console = 0;
                         }
                 }
@@ -1178,64 +1217,62 @@ void register_console(struct console *console)
          */
         for (i = 0; i < MAX_CMDLINECONSOLES && console_cmdline[i].name[0];
                         i++) {
-                if (strcmp(console_cmdline[i].name, console->name) != 0)
+                if (strcmp(console_cmdline[i].name, newcon->name) != 0)
                         continue;
-                if (console->index >= 0 &&
-                    console->index != console_cmdline[i].index)
+                if (newcon->index >= 0 &&
+                    newcon->index != console_cmdline[i].index)
                         continue;
-                if (console->index < 0)
-                        console->index = console_cmdline[i].index;
+                if (newcon->index < 0)
+                        newcon->index = console_cmdline[i].index;
 #ifdef CONFIG_A11Y_BRAILLE_CONSOLE
                 if (console_cmdline[i].brl_options) {
-                        console->flags |= CON_BRL;
-                        braille_register_console(console,
+                        newcon->flags |= CON_BRL;
+                        braille_register_console(newcon,
                                         console_cmdline[i].index,
                                         console_cmdline[i].options,
                                         console_cmdline[i].brl_options);
                         return;
                 }
 #endif
-                if (console->setup &&
-                    console->setup(console, console_cmdline[i].options) != 0)
+                if (newcon->setup &&
+                    newcon->setup(newcon, console_cmdline[i].options) != 0)
                         break;
-                console->flags |= CON_ENABLED;
-                console->index = console_cmdline[i].index;
+                newcon->flags |= CON_ENABLED;
+                newcon->index = console_cmdline[i].index;
                 if (i == selected_console) {
-                        console->flags |= CON_CONSDEV;
+                        newcon->flags |= CON_CONSDEV;
                         preferred_console = selected_console;
                 }
                 break;
         }
 
-        if (!(console->flags & CON_ENABLED))
+        if (!(newcon->flags & CON_ENABLED))
                 return;
 
-        if (bootconsole && (console->flags & CON_CONSDEV)) {
-                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;
-        } else {
-                printk(KERN_INFO "console [%s%d] enabled\n",
-                       console->name, console->index);
-        }
+        /*
+         * If we have a bootconsole, and are switching to a real console,
+         * don't print everything out again, since when the boot console, and
+         * the real console are the same physical device, it's annoying to
+         * see the beginning boot messages twice
+         */
+        if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV))
+                newcon->flags &= ~CON_PRINTBUFFER;
 
         /*
          *      Put this console in the list - keep the
          *      preferred driver at the head of the list.
          */
         acquire_console_sem();
-        if ((console->flags & CON_CONSDEV) || console_drivers == NULL) {
-                console->next = console_drivers;
-                console_drivers = console;
-                if (console->next)
-                        console->next->flags &= ~CON_CONSDEV;
+        if ((newcon->flags & CON_CONSDEV) || console_drivers == NULL) {
+                newcon->next = console_drivers;
+                console_drivers = newcon;
+                if (newcon->next)
+                        newcon->next->flags &= ~CON_CONSDEV;
         } else {
-                console->next = console_drivers->next;
-                console_drivers->next = console;
+                newcon->next = console_drivers->next;
+                console_drivers->next = newcon;
         }
-        if (console->flags & CON_PRINTBUFFER) {
+        if (newcon->flags & CON_PRINTBUFFER) {
                 /*
                  * release_console_sem() will print out the buffered messages
                  * for us.
@@ -1245,6 +1282,28 @@ void register_console(struct console *console)
                 spin_unlock_irqrestore(&logbuf_lock, flags);
         }
         release_console_sem();
+
+        /*
+         * By unregistering the bootconsoles after we enable the real console
+         * we get the "console xxx enabled" message on all the consoles -
+         * boot consoles, real consoles, etc - this is to ensure that end
+         * users know there might be something in the kernel's log buffer that
+         * went to the bootconsole (that they do not see on the real console)
+         */
+        if (bcon && ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV)) {
+                /* we need to iterate through twice, to make sure we print
+                 * everything out, before we unregister the console(s)
+                 */
+                printk(KERN_INFO "console [%s%d] enabled, bootconsole disabled\n",
+                        newcon->name, newcon->index);
+                for_each_console(bcon)
+                        if (bcon->flags & CON_BOOT)
+                                unregister_console(bcon);
+        } else {
+                printk(KERN_INFO "%sconsole [%s%d] enabled\n",
+                        (newcon->flags & CON_BOOT) ? "boot" : "" ,
+                        newcon->name, newcon->index);
+        }
 }
 EXPORT_SYMBOL(register_console);
 
@@ -1287,11 +1346,13 @@ EXPORT_SYMBOL(unregister_console);
 
 static int __init disable_boot_consoles(void)
 {
-        if (console_drivers != NULL) {
-                if (console_drivers->flags & CON_BOOT) {
+        struct console *con;
+
+        for_each_console(con) {
+                if (con->flags & CON_BOOT) {
                         printk(KERN_INFO "turn off boot console %s%d\n",
-                                console_drivers->name, console_drivers->index);
-                        return unregister_console(console_drivers);
+                                con->name, con->index);
+                        unregister_console(con);
                 }
         }
         return 0;