---

yaml
---
r: 29696
b: refs/heads/master
c: 76a8ad2
h: refs/heads/master
v: v3

[refs]

@@ -1,2 +1,2 @@
 ---
-refs/heads/master: 8ae6e163c1b637e1cb125613726ffbd31ca44fdf
+refs/heads/master: 76a8ad293912cd2f01eca075d80cd0ddec30c627

trunk/include/linux/console.h

@@ -87,6 +87,7 @@ void give_up_console(const struct consw *sw);
 #define CON_CONSDEV	(2) /* Last on the command line */
 #define CON_ENABLED	(4)
 #define CON_BOOT	(8)
+#define CON_ANYTIME	(16) /* Safe to call when cpu is offline */
 
 struct console
 {

trunk/kernel/printk.c

@@ -327,7 +327,9 @@ static void __call_console_drivers(unsigned long start, unsigned long end)
 	struct console *con;
 
 	for (con = console_drivers; con; con = con->next) {
-		if ((con->flags & CON_ENABLED) && con->write)
+		if ((con->flags & CON_ENABLED) && con->write &&
+				(cpu_online(smp_processor_id()) ||
+				(con->flags & CON_ANYTIME)))
 			con->write(con, &LOG_BUF(start), end - start);
 	}
 }
@@ -453,6 +455,18 @@ __attribute__((weak)) unsigned long long printk_clock(void)
 	return sched_clock();
 }
 
+/* Check if we have any console registered that can be called early in boot. */
+static int have_callable_console(void)
+{
+	struct console *con;
+
+	for (con = console_drivers; con; con = con->next)
+		if (con->flags & CON_ANYTIME)
+			return 1;
+
+	return 0;
+}
+
 /**
  * printk - print a kernel message
  * @fmt: format string
@@ -566,27 +580,29 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 			log_level_unknown = 1;
 	}
 
-	if (!cpu_online(smp_processor_id())) {
+	if (!down_trylock(&console_sem)) {
 		/*
-		 * Some console drivers may assume that per-cpu resources have
-		 * been allocated.  So don't allow them to be called by this
-		 * CPU until it is officially up.  We shouldn't be calling into
-		 * random console drivers on a CPU which doesn't exist yet..
+		 * We own the drivers.  We can drop the spinlock and
+		 * let release_console_sem() print the text, maybe ...
 		 */
+		console_locked = 1;
 		printk_cpu = UINT_MAX;
 		spin_unlock_irqrestore(&logbuf_lock, flags);
-		goto out;
-	}
-	if (!down_trylock(&console_sem)) {
-		console_locked = 1;
+
 		/*
-		 * We own the drivers.  We can drop the spinlock and let
-		 * release_console_sem() print the text
+		 * Console drivers may assume that per-cpu resources have
+		 * been allocated. So unless they're explicitly marked as
+		 * being able to cope (CON_ANYTIME) don't call them until
+		 * this CPU is officially up.
 		 */
-		printk_cpu = UINT_MAX;
-		spin_unlock_irqrestore(&logbuf_lock, flags);
-		console_may_schedule = 0;
-		release_console_sem();
+		if (cpu_online(smp_processor_id()) || have_callable_console()) {
+			console_may_schedule = 0;
+			release_console_sem();
+		} else {
+			/* Release by hand to avoid flushing the buffer. */
+			console_locked = 0;
+			up(&console_sem);
+		}
 	} else {
 		/*
 		 * Someone else owns the drivers.  We drop the spinlock, which
@@ -596,7 +612,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 		printk_cpu = UINT_MAX;
 		spin_unlock_irqrestore(&logbuf_lock, flags);
 	}
-out:
+
 	preempt_enable();
 	return printed_len;
 }