locking/lockdep: Fix ->irq_context calculation

task_irq_context() returns the encoded irq_context of the task, the
return value is encoded in the same as ->irq_context of held_lock.

Always return 0 if !(CONFIG_TRACE_IRQFLAGS && CONFIG_PROVE_LOCKING)

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: sasha.levin@oracle.com
Link: http://lkml.kernel.org/r/1455602265-16490-2-git-send-email-boqun.feng@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/locking/lockdep.c

@@ -2932,6 +2932,11 @@ static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
 	return 1;
 }
 
+static inline unsigned int task_irq_context(struct task_struct *task)
+{
+	return 2 * !!task->hardirq_context + !!task->softirq_context;
+}
+
 static int separate_irq_context(struct task_struct *curr,
 		struct held_lock *hlock)
 {
@@ -2940,8 +2945,6 @@ static int separate_irq_context(struct task_struct *curr,
 	/*
 	 * Keep track of points where we cross into an interrupt context:
 	 */
-	hlock->irq_context = 2*(curr->hardirq_context ? 1 : 0) +
-				curr->softirq_context;
 	if (depth) {
 		struct held_lock *prev_hlock;
 
@@ -2973,6 +2976,11 @@ static inline int mark_irqflags(struct task_struct *curr,
 	return 1;
 }
 
+static inline unsigned int task_irq_context(struct task_struct *task)
+{
+	return 0;
+}
+
 static inline int separate_irq_context(struct task_struct *curr,
 		struct held_lock *hlock)
 {
@@ -3241,6 +3249,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 	hlock->acquire_ip = ip;
 	hlock->instance = lock;
 	hlock->nest_lock = nest_lock;
+	hlock->irq_context = task_irq_context(curr);
 	hlock->trylock = trylock;
 	hlock->read = read;
 	hlock->check = check;