printk: fix lockdep instrumentation of console_sem

Printk calls mutex_acquire() / mutex_release() by hand to instrument
lockdep about console_sem.  However in some corner cases the
instrumentation is missing.  Fix the problem by creating helper functions
for locking / unlocking console_sem which take care of lockdep
instrumentation as well.

Signed-off-by: Jan Kara <jack@suse.cz>
Reported-by: Fabio Estevam <festevam@gmail.com>
Reported-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Tested-by: Fabio Estevam <fabio.estevam@freescale.com>
Tested-By: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
index 6e1b21a..5ba37f8 100644 (file)
--- a/kernel/printk/printk.c
+++ b/kernel/printk/printk.c
@@ -90,6 +90,29 @@ static struct lockdep_map console_lock_dep_map = {
 };
 #endif
 
+/*
+ * Helper macros to handle lockdep when locking/unlocking console_sem. We use
+ * macros instead of functions so that _RET_IP_ contains useful information.
+ */
+#define down_console_sem() do { \
+       down(&console_sem);\
+       mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);\
+} while (0)
+
+static int __down_trylock_console_sem(unsigned long ip)
+{
+       if (down_trylock(&console_sem))
+               return 1;
+       mutex_acquire(&console_lock_dep_map, 0, 1, ip);
+       return 0;
+}
+#define down_trylock_console_sem() __down_trylock_console_sem(_RET_IP_)
+
+#define up_console_sem() do { \
+       mutex_release(&console_lock_dep_map, 1, _RET_IP_);\
+       up(&console_sem);\
+} while (0)
+
 /*
  * This is used for debugging the mess that is the VT code by
  * keeping track if we have the console semaphore held. It's
@@ -1422,7 +1445,7 @@ static int console_trylock_for_printk(unsigned int cpu)
         */
        if (!can_use_console(cpu)) {
                console_locked = 0;
-               up(&console_sem);
+               up_console_sem();
                return 0;
        }
        return 1;
@@ -1951,16 +1974,14 @@ void suspend_console(void)
        printk("Suspending console(s) (use no_console_suspend to debug)\n");
        console_lock();
        console_suspended = 1;
-       up(&console_sem);
-       mutex_release(&console_lock_dep_map, 1, _RET_IP_);
+       up_console_sem();
 }
 
 void resume_console(void)
 {
        if (!console_suspend_enabled)
                return;
-       down(&console_sem);
-       mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);
+       down_console_sem();
        console_suspended = 0;
        console_unlock();
 }
@@ -2002,12 +2023,11 @@ void console_lock(void)
 {
        might_sleep();
 
-       down(&console_sem);
+       down_console_sem();
        if (console_suspended)
                return;
        console_locked = 1;
        console_may_schedule = 1;
-       mutex_acquire(&console_lock_dep_map, 0, 0, _RET_IP_);
 }
 EXPORT_SYMBOL(console_lock);
 
@@ -2021,15 +2041,14 @@ EXPORT_SYMBOL(console_lock);
  */
 int console_trylock(void)
 {
-       if (down_trylock(&console_sem))
+       if (down_trylock_console_sem())
                return 0;
        if (console_suspended) {
-               up(&console_sem);
+               up_console_sem();
                return 0;
        }
        console_locked = 1;
        console_may_schedule = 0;
-       mutex_acquire(&console_lock_dep_map, 0, 1, _RET_IP_);
        return 1;
 }
 EXPORT_SYMBOL(console_trylock);
@@ -2091,7 +2110,7 @@ void console_unlock(void)
        bool retry;
 
        if (console_suspended) {
-               up(&console_sem);
+               up_console_sem();
                return;
        }
 
@@ -2153,7 +2172,6 @@ skip:
                local_irq_restore(flags);
        }
        console_locked = 0;
-       mutex_release(&console_lock_dep_map, 1, _RET_IP_);
 
        /* Release the exclusive_console once it is used */
        if (unlikely(exclusive_console))
@@ -2161,7 +2179,7 @@ skip:
 
        raw_spin_unlock(&logbuf_lock);
 
-       up(&console_sem);
+       up_console_sem();
 
        /*
         * Someone could have filled up the buffer again, so re-check if there's
@@ -2206,7 +2224,7 @@ void console_unblank(void)
         * oops_in_progress is set to 1..
         */
        if (oops_in_progress) {
-               if (down_trylock(&console_sem) != 0)
+               if (down_trylock_console_sem() != 0)
                        return;
        } else
                console_lock();