[RFC 1/6] lockdep: Add helper functions of irq_context

[Boqun Feng <boqun.feng@gmail.com>]

Add two helper functions of irq_context:

task_irq_context(): return 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)

is_same_irq_context(): compare whether two irq_context are the same.
Always return true if !(CONFIG_TRACE_IRQFLAGS && CONFIG_PROVE_LOCKING)

These two functions are added for the future use of irq_context by
LOCKED_ACCESS, because LOCKED_ACCESS needs to get the irq_context value
of a task when a data access happens rather than when a lock is
acquired, so it needs another way than getting the value from
held_lock::irq_context

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
---
 kernel/locking/lockdep.c | 23 +++++++++++++++++++++--
 1 file changed, 21 insertions(+), 2 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 60ace56..c8a632b 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2839,6 +2839,16 @@ static int mark_irqflags(struct task_struct *curr, struct held_lock *hlock)
 	return 1;
 }
 
+static unsigned int task_irq_context(struct task_struct *task)
+{
+	return 2 * (task->hardirq_context ? 1 : 0) + task->softirq_context;
+}
+
+static bool is_same_irq_context(unsigned int ctx1, unsigned int ctx2)
+{
+	return ctx1 == ctx2;
+}
+
 static int separate_irq_context(struct task_struct *curr,
 		struct held_lock *hlock)
 {
@@ -2847,8 +2857,7 @@ 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;
+	hlock->irq_context = task_irq_context(curr);
 	if (depth) {
 		struct held_lock *prev_hlock;
 
@@ -2880,6 +2889,16 @@ static inline int mark_irqflags(struct task_struct *curr,
 	return 1;
 }
 
+static unsigned int task_irq_context(struct task_struct *task)
+{
+	return 0;
+}
+
+static bool is_same_irq_context(unsigned int ctx1, unsigned int ctx2)
+{
+	return true;
+}
+
 static inline int separate_irq_context(struct task_struct *curr,
 		struct held_lock *hlock)
 {
-- 
2.7.0