Merge branch 'core-printk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip

* 'core-printk-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/linux-2.6-tip:
  lockdep: Fix trace_[soft,hard]irqs_[on,off]() recursion
  printk: Fix console_sem vs logbuf_lock unlock race
  printk: Release console_sem after logbuf_lock

2 files changed, 41 insertions, 13 deletions

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 628276d05915..3956f5149e25 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -2481,15 +2481,10 @@ mark_held_locks(struct task_struct *curr, enum mark_type mark)
 /*
  * Hardirqs will be enabled:
  */
-void trace_hardirqs_on_caller(unsigned long ip)
+static void __trace_hardirqs_on_caller(unsigned long ip)
 {
 	struct task_struct *curr = current;
 
-	time_hardirqs_on(CALLER_ADDR0, ip);
-
-	if (unlikely(!debug_locks || current->lockdep_recursion))
-		return;
-
 	if (DEBUG_LOCKS_WARN_ON(unlikely(early_boot_irqs_disabled)))
 		return;
 
@@ -2505,8 +2500,6 @@ void trace_hardirqs_on_caller(unsigned long ip)
 	/* we'll do an OFF -> ON transition: */
 	curr->hardirqs_enabled = 1;
 
-	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
-		return;
 	if (DEBUG_LOCKS_WARN_ON(current->hardirq_context))
 		return;
 	/*
@@ -2528,6 +2521,21 @@ void trace_hardirqs_on_caller(unsigned long ip)
 	curr->hardirq_enable_event = ++curr->irq_events;
 	debug_atomic_inc(hardirqs_on_events);
 }
+
+void trace_hardirqs_on_caller(unsigned long ip)
+{
+	time_hardirqs_on(CALLER_ADDR0, ip);
+
+	if (unlikely(!debug_locks || current->lockdep_recursion))
+		return;
+
+	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
+		return;
+
+	current->lockdep_recursion = 1;
+	__trace_hardirqs_on_caller(ip);
+	current->lockdep_recursion = 0;
+}
 EXPORT_SYMBOL(trace_hardirqs_on_caller);
 
 void trace_hardirqs_on(void)
@@ -2577,7 +2585,7 @@ void trace_softirqs_on(unsigned long ip)
 {
 	struct task_struct *curr = current;
 
-	if (unlikely(!debug_locks))
+	if (unlikely(!debug_locks || current->lockdep_recursion))
 		return;
 
 	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
@@ -2588,6 +2596,7 @@ void trace_softirqs_on(unsigned long ip)
 		return;
 	}
 
+	current->lockdep_recursion = 1;
 	/*
 	 * We'll do an OFF -> ON transition:
 	 */
@@ -2602,6 +2611,7 @@ void trace_softirqs_on(unsigned long ip)
 	 */
 	if (curr->hardirqs_enabled)
 		mark_held_locks(curr, SOFTIRQ);
+	current->lockdep_recursion = 0;
 }
 
 /*
@@ -2611,7 +2621,7 @@ void trace_softirqs_off(unsigned long ip)
 {
 	struct task_struct *curr = current;
 
-	if (unlikely(!debug_locks))
+	if (unlikely(!debug_locks || current->lockdep_recursion))
 		return;
 
 	if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
diff --git a/kernel/printk.c b/kernel/printk.c
index 35185392173f..37dff3429adb 100644
--- a/kernel/printk.c
+++ b/kernel/printk.c
@@ -782,7 +782,7 @@ static inline int can_use_console(unsigned int cpu)
 static int console_trylock_for_printk(unsigned int cpu)
 	__releases(&logbuf_lock)
 {
-	int retval = 0;
+	int retval = 0, wake = 0;
 
 	if (console_trylock()) {
 		retval = 1;
@@ -795,12 +795,14 @@ static int console_trylock_for_printk(unsigned int cpu)
 		 */
 		if (!can_use_console(cpu)) {
 			console_locked = 0;
-			up(&console_sem);
+			wake = 1;
 			retval = 0;
 		}
 	}
 	printk_cpu = UINT_MAX;
 	spin_unlock(&logbuf_lock);
+	if (wake)
+		up(&console_sem);
 	return retval;
 }
 static const char recursion_bug_msg [] =
@@ -1242,7 +1244,7 @@ void console_unlock(void)
 {
 	unsigned long flags;
 	unsigned _con_start, _log_end;
-	unsigned wake_klogd = 0;
+	unsigned wake_klogd = 0, retry = 0;
 
 	if (console_suspended) {
 		up(&console_sem);
@@ -1251,6 +1253,7 @@ void console_unlock(void)
 
 	console_may_schedule = 0;
 
+again:
 	for ( ; ; ) {
 		spin_lock_irqsave(&logbuf_lock, flags);
 		wake_klogd |= log_start - log_end;
@@ -1271,8 +1274,23 @@ void console_unlock(void)
 	if (unlikely(exclusive_console))
 		exclusive_console = NULL;
 
+	spin_unlock(&logbuf_lock);
+
 	up(&console_sem);
+
+	/*
+	 * Someone could have filled up the buffer again, so re-check if there's
+	 * something to flush. In case we cannot trylock the console_sem again,
+	 * there's a new owner and the console_unlock() from them will do the
+	 * flush, no worries.
+	 */
+	spin_lock(&logbuf_lock);
+	if (con_start != log_end)
+		retry = 1;
 	spin_unlock_irqrestore(&logbuf_lock, flags);
+	if (retry && console_trylock())
+		goto again;
+
 	if (wake_klogd)
 		wake_up_klogd();
 }