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();
 }