locking, printk: Annotate logbuf_lock as raw

The logbuf_lock lock can be taken in atomic context and therefore
cannot be preempted on -rt - annotate it.

In mainline this change documents the low level nature of
the lock - otherwise there's no functional difference. Lockdep
and Sparse checking will work as usual.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[ merged and fixed it ]
Signed-off-by: Ingo Molnar <mingo@elte.hu>

include/linux/ratelimit.h

@@ -8,7 +8,7 @@
 #define DEFAULT_RATELIMIT_BURST		10
 
 struct ratelimit_state {
-	spinlock_t	lock;		/* protect the state */
+	raw_spinlock_t	lock;		/* protect the state */
 
 	int		interval;
 	int		burst;
@@ -20,7 +20,7 @@ struct ratelimit_state {
 #define DEFINE_RATELIMIT_STATE(name, interval_init, burst_init)		\
 									\
 	struct ratelimit_state name = {					\
-		.lock		= __SPIN_LOCK_UNLOCKED(name.lock),	\
+		.lock		= __RAW_SPIN_LOCK_UNLOCKED(name.lock),	\
 		.interval	= interval_init,			\
 		.burst		= burst_init,				\
 	}
@@ -28,7 +28,7 @@ struct ratelimit_state {
 static inline void ratelimit_state_init(struct ratelimit_state *rs,
 					int interval, int burst)
 {
-	spin_lock_init(&rs->lock);
+	raw_spin_lock_init(&rs->lock);
 	rs->interval = interval;
 	rs->burst = burst;
 	rs->printed = 0;

kernel/printk.c

@@ -100,7 +100,7 @@ static int console_locked, console_suspended;
  * It is also used in interesting ways to provide interlocking in
  * console_unlock();.
  */
-static DEFINE_SPINLOCK(logbuf_lock);
+static DEFINE_RAW_SPINLOCK(logbuf_lock);
 
 #define LOG_BUF_MASK (log_buf_len-1)
 #define LOG_BUF(idx) (log_buf[(idx) & LOG_BUF_MASK])
@@ -212,7 +212,7 @@ void __init setup_log_buf(int early)
 		return;
 	}
 
-	spin_lock_irqsave(&logbuf_lock, flags);
+	raw_spin_lock_irqsave(&logbuf_lock, flags);
 	log_buf_len = new_log_buf_len;
 	log_buf = new_log_buf;
 	new_log_buf_len = 0;
@@ -230,7 +230,7 @@ void __init setup_log_buf(int early)
 	log_start -= offset;
 	con_start -= offset;
 	log_end -= offset;
-	spin_unlock_irqrestore(&logbuf_lock, flags);
+	raw_spin_unlock_irqrestore(&logbuf_lock, flags);
 
 	pr_info("log_buf_len: %d\n", log_buf_len);
 	pr_info("early log buf free: %d(%d%%)\n",
@@ -365,18 +365,18 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
 		if (error)
 			goto out;
 		i = 0;
-		spin_lock_irq(&logbuf_lock);
+		raw_spin_lock_irq(&logbuf_lock);
 		while (!error && (log_start != log_end) && i < len) {
 			c = LOG_BUF(log_start);
 			log_start++;
-			spin_unlock_irq(&logbuf_lock);
+			raw_spin_unlock_irq(&logbuf_lock);
 			error = __put_user(c,buf);
 			buf++;
 			i++;
 			cond_resched();
-			spin_lock_irq(&logbuf_lock);
+			raw_spin_lock_irq(&logbuf_lock);
 		}
-		spin_unlock_irq(&logbuf_lock);
+		raw_spin_unlock_irq(&logbuf_lock);
 		if (!error)
 			error = i;
 		break;
@@ -399,7 +399,7 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
 		count = len;
 		if (count > log_buf_len)
 			count = log_buf_len;
-		spin_lock_irq(&logbuf_lock);
+		raw_spin_lock_irq(&logbuf_lock);
 		if (count > logged_chars)
 			count = logged_chars;
 		if (do_clear)
@@ -416,12 +416,12 @@ int do_syslog(int type, char __user *buf, int len, bool from_file)
 			if (j + log_buf_len < log_end)
 				break;
 			c = LOG_BUF(j);
-			spin_unlock_irq(&logbuf_lock);
+			raw_spin_unlock_irq(&logbuf_lock);
 			error = __put_user(c,&buf[count-1-i]);
 			cond_resched();
-			spin_lock_irq(&logbuf_lock);
+			raw_spin_lock_irq(&logbuf_lock);
 		}
-		spin_unlock_irq(&logbuf_lock);
+		raw_spin_unlock_irq(&logbuf_lock);
 		if (error)
 			break;
 		error = i;
@@ -689,7 +689,7 @@ static void zap_locks(void)
 	oops_timestamp = jiffies;
 
 	/* If a crash is occurring, make sure we can't deadlock */
-	spin_lock_init(&logbuf_lock);
+	raw_spin_lock_init(&logbuf_lock);
 	/* And make sure that we print immediately */
 	sema_init(&console_sem, 1);
 }
@@ -802,9 +802,9 @@ static int console_trylock_for_printk(unsigned int cpu)
 		}
 	}
 	printk_cpu = UINT_MAX;
-	spin_unlock(&logbuf_lock);
 	if (wake)
 		up(&console_sem);
+	raw_spin_unlock(&logbuf_lock);
 	return retval;
 }
 static const char recursion_bug_msg [] =
@@ -864,7 +864,7 @@ asmlinkage int vprintk(const char *fmt, va_list args)
 	}
 
 	lockdep_off();
-	spin_lock(&logbuf_lock);
+	raw_spin_lock(&logbuf_lock);
 	printk_cpu = this_cpu;
 
 	if (recursion_bug) {
@@ -1257,14 +1257,14 @@ void console_unlock(void)
 
 again:
 	for ( ; ; ) {
-		spin_lock_irqsave(&logbuf_lock, flags);
+		raw_spin_lock_irqsave(&logbuf_lock, flags);
 		wake_klogd |= log_start - log_end;
 		if (con_start == log_end)
 			break;			/* Nothing to print */
 		_con_start = con_start;
 		_log_end = log_end;
 		con_start = log_end;		/* Flush */
-		spin_unlock(&logbuf_lock);
+		raw_spin_unlock(&logbuf_lock);
 		stop_critical_timings();	/* don't trace print latency */
 		call_console_drivers(_con_start, _log_end);
 		start_critical_timings();
@@ -1276,7 +1276,7 @@ again:
 	if (unlikely(exclusive_console))
 		exclusive_console = NULL;
 
-	spin_unlock(&logbuf_lock);
+	raw_spin_unlock(&logbuf_lock);
 
 	up(&console_sem);
 
@@ -1286,13 +1286,13 @@ again:
 	 * there's a new owner and the console_unlock() from them will do the
 	 * flush, no worries.
 	 */
-	spin_lock(&logbuf_lock);
+	raw_spin_lock(&logbuf_lock);
 	if (con_start != log_end)
 		retry = 1;
-	spin_unlock_irqrestore(&logbuf_lock, flags);
 	if (retry && console_trylock())
 		goto again;
 
+	raw_spin_unlock_irqrestore(&logbuf_lock, flags);
 	if (wake_klogd)
 		wake_up_klogd();
 }
@@ -1522,9 +1522,9 @@ void register_console(struct console *newcon)
 		 * console_unlock(); will print out the buffered messages
 		 * for us.
 		 */
-		spin_lock_irqsave(&logbuf_lock, flags);
+		raw_spin_lock_irqsave(&logbuf_lock, flags);
 		con_start = log_start;
-		spin_unlock_irqrestore(&logbuf_lock, flags);
+		raw_spin_unlock_irqrestore(&logbuf_lock, flags);
 		/*
 		 * We're about to replay the log buffer.  Only do this to the
 		 * just-registered console to avoid excessive message spam to
@@ -1731,10 +1731,10 @@ void kmsg_dump(enum kmsg_dump_reason reason)
 	/* Theoretically, the log could move on after we do this, but
 	   there's not a lot we can do about that. The new messages
 	   will overwrite the start of what we dump. */
-	spin_lock_irqsave(&logbuf_lock, flags);
+	raw_spin_lock_irqsave(&logbuf_lock, flags);
 	end = log_end & LOG_BUF_MASK;
 	chars = logged_chars;
-	spin_unlock_irqrestore(&logbuf_lock, flags);
+	raw_spin_unlock_irqrestore(&logbuf_lock, flags);
 
 	if (chars > end) {
 		s1 = log_buf + log_buf_len - chars + end;

lib/ratelimit.c

@@ -39,7 +39,7 @@ int ___ratelimit(struct ratelimit_state *rs, const char *func)
 	 * in addition to the one that will be printed by
 	 * the entity that is holding the lock already:
 	 */
-	if (!spin_trylock_irqsave(&rs->lock, flags))
+	if (!raw_spin_trylock_irqsave(&rs->lock, flags))
 		return 0;
 
 	if (!rs->begin)
@@ -60,7 +60,7 @@ int ___ratelimit(struct ratelimit_state *rs, const char *func)
 		rs->missed++;
 		ret = 0;
 	}
-	spin_unlock_irqrestore(&rs->lock, flags);
+	raw_spin_unlock_irqrestore(&rs->lock, flags);
 
 	return ret;
 }