1 files changed, 34 insertions, 2 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index 33284adb2189..da8ca817eae3 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -53,7 +53,7 @@ void asmlinkage __attribute__((weak)) early_printk(const char *fmt, ...)
 #define __LOG_BUF_LEN   (1 << CONFIG_LOG_BUF_SHIFT)
 
 /* printk's without a loglevel use this.. */
-#define DEFAULT_MESSAGE_LOGLEVEL 4 /* KERN_WARNING */
+#define DEFAULT_MESSAGE_LOGLEVEL CONFIG_DEFAULT_MESSAGE_LOGLEVEL
 
 /* We show everything that is MORE important than this.. */
 #define MINIMUM_CONSOLE_LOGLEVEL 1 /* Minimum loglevel we let people use */
@@ -113,6 +113,11 @@ static unsigned con_start;	/* Index into log_buf: next char to be sent to consol
 static unsigned log_end;        /* Index into log_buf: most-recently-written-char + 1 */
 
 /*
+ * If exclusive_console is non-NULL then only this console is to be printed to.
+ */
+static struct console *exclusive_console;
+
+/*
  *      Array of consoles built from command line options (console=)
  */
 struct console_cmdline
@@ -476,6 +481,8 @@ static void __call_console_drivers(unsigned start, unsigned end)
         struct console *con;
 
         for_each_console(con) {
+                if (exclusive_console && con != exclusive_console)
+                        continue;
                 if ((con->flags & CON_ENABLED) && con->write &&
                                 (cpu_online(smp_processor_id()) ||
                                 (con->flags & CON_ANYTIME)))
@@ -1230,6 +1237,11 @@ void console_unlock(void)
                 local_irq_restore(flags);
         }
         console_locked = 0;
+
+        /* Release the exclusive_console once it is used */
+        if (unlikely(exclusive_console))
+                exclusive_console = NULL;
+
         up(&console_sem);
         spin_unlock_irqrestore(&logbuf_lock, flags);
         if (wake_klogd)
@@ -1316,6 +1328,18 @@ void console_start(struct console *console)
 }
 EXPORT_SYMBOL(console_start);
 
+static int __read_mostly keep_bootcon;
+
+static int __init keep_bootcon_setup(char *str)
+{
+        keep_bootcon = 1;
+        printk(KERN_INFO "debug: skip boot console de-registration.\n");
+
+        return 0;
+}
+
+early_param("keep_bootcon", keep_bootcon_setup);
+
 /*
  * The console driver calls this routine during kernel initialization
  * to register the console printing procedure with printk() and to
@@ -1452,6 +1476,12 @@ void register_console(struct console *newcon)
                 spin_lock_irqsave(&logbuf_lock, flags);
                 con_start = log_start;
                 spin_unlock_irqrestore(&logbuf_lock, flags);
+                /*
+                 * We're about to replay the log buffer.  Only do this to the
+                 * just-registered console to avoid excessive message spam to
+                 * the already-registered consoles.
+                 */
+                exclusive_console = newcon;
         }
         console_unlock();
         console_sysfs_notify();
@@ -1463,7 +1493,9 @@ void register_console(struct console *newcon)
          * 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)) {
+        if (bcon &&
+            ((newcon->flags & (CON_CONSDEV | CON_BOOT)) == CON_CONSDEV) &&
+            !keep_bootcon) {
                 /* we need to iterate through twice, to make sure we print
                  * everything out, before we unregister the console(s)
                  */