1 files changed, 61 insertions, 7 deletions

diff --git a/kernel/printk.c b/kernel/printk.c
index 75077ad0b53..8fe465ac008 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -33,9 +33,12 @@
 #include <linux/bootmem.h>
 #include <linux/syscalls.h>
 #include <linux/kexec.h>
+#include <linux/kdb.h>
 #include <linux/ratelimit.h>
 #include <linux/kmsg_dump.h>
 #include <linux/syslog.h>
+#include <linux/cpu.h>
+#include <linux/notifier.h>
 
 #include <asm/uaccess.h>
 
@@ -413,6 +416,22 @@ SYSCALL_DEFINE3(syslog, int, type, char __user *, buf, int, len)
 	return do_syslog(type, buf, len, SYSLOG_FROM_CALL);
 }
 
+#ifdef	CONFIG_KGDB_KDB
+/* kdb dmesg command needs access to the syslog buffer.  do_syslog()
+ * uses locks so it cannot be used during debugging.  Just tell kdb
+ * where the start and end of the physical and logical logs are.  This
+ * is equivalent to do_syslog(3).
+ */
+void kdb_syslog_data(char *syslog_data[4])
+{
+	syslog_data[0] = log_buf;
+	syslog_data[1] = log_buf + log_buf_len;
+	syslog_data[2] = log_buf + log_end -
+		(logged_chars < log_buf_len ? logged_chars : log_buf_len);
+	syslog_data[3] = log_buf + log_end;
+}
+#endif	/* CONFIG_KGDB_KDB */
+
 /*
  * Call the console drivers on a range of log_buf
  */
@@ -586,6 +605,14 @@ asmlinkage int printk(const char *fmt, ...)
 	va_list args;
 	int r;
 
+#ifdef CONFIG_KGDB_KDB
+	if (unlikely(kdb_trap_printk)) {
+		va_start(args, fmt);
+		r = vkdb_printf(fmt, args);
+		va_end(args);
+		return r;
+	}
+#endif
 	va_start(args, fmt);
 	r = vprintk(fmt, args);
 	va_end(args);
@@ -960,6 +987,32 @@ void resume_console(void)
 }
 
 /**
+ * console_cpu_notify - print deferred console messages after CPU hotplug
+ * @self: notifier struct
+ * @action: CPU hotplug event
+ * @hcpu: unused
+ *
+ * If printk() is called from a CPU that is not online yet, the messages
+ * will be spooled but will not show up on the console.  This function is
+ * called when a new CPU comes online (or fails to come up), and ensures
+ * that any such output gets printed.
+ */
+static int __cpuinit console_cpu_notify(struct notifier_block *self,
+	unsigned long action, void *hcpu)
+{
+	switch (action) {
+	case CPU_ONLINE:
+	case CPU_DEAD:
+	case CPU_DYING:
+	case CPU_DOWN_FAILED:
+	case CPU_UP_CANCELED:
+		acquire_console_sem();
+		release_console_sem();
+	}
+	return NOTIFY_OK;
+}
+
+/**
  * acquire_console_sem - lock the console system for exclusive use.
  *
  * Acquires a semaphore which guarantees that the caller has
@@ -1346,7 +1399,7 @@ int unregister_console(struct console *console)
 }
 EXPORT_SYMBOL(unregister_console);
 
-static int __init disable_boot_consoles(void)
+static int __init printk_late_init(void)
 {
 	struct console *con;
 
@@ -1357,9 +1410,10 @@ static int __init disable_boot_consoles(void)
 			unregister_console(con);
 		}
 	}
+	hotcpu_notifier(console_cpu_notify, 0);
 	return 0;
 }
-late_initcall(disable_boot_consoles);
+late_initcall(printk_late_init);
 
 #if defined CONFIG_PRINTK
 
@@ -1495,9 +1549,9 @@ void kmsg_dump(enum kmsg_dump_reason reason)
 	chars = logged_chars;
 	spin_unlock_irqrestore(&logbuf_lock, flags);
 
-	if (logged_chars > end) {
-		s1 = log_buf + log_buf_len - logged_chars + end;
-		l1 = logged_chars - end;
+	if (chars > end) {
+		s1 = log_buf + log_buf_len - chars + end;
+		l1 = chars - end;
 
 		s2 = log_buf;
 		l2 = end;
@@ -1505,8 +1559,8 @@ void kmsg_dump(enum kmsg_dump_reason reason)
 		s1 = "";
 		l1 = 0;
 
-		s2 = log_buf + end - logged_chars;
-		l2 = logged_chars;
+		s2 = log_buf + end - chars;
+		l2 = chars;
 	}
 
 	if (!spin_trylock_irqsave(&dump_list_lock, flags)) {