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Subject[PATCH 5/6] lockdep: Prepare for NMI IRQ state tracking
There is no reason not to always, accurately, track IRQ state.

This change also makes IRQ state tracking ignore lockdep_off().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/locking/lockdep.c | 23 ++++++++++++++++-------
1 file changed, 16 insertions(+), 7 deletions(-)

--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3646,7 +3646,12 @@ static void __trace_hardirqs_on_caller(v
*/
void lockdep_hardirqs_on_prepare(unsigned long ip)
{
- if (unlikely(!debug_locks || current->lockdep_recursion))
+ /*
+ * Even though NMIs can happen while in lockdep; we only call this
+ * then the NMI returns to an IRQs enabled context, which guarantees
+ * we're not in lockdep.
+ */
+ if (DEBUG_LOCKS_WARN_ON(current->lockdep_recursion & LOCKDEP_RECURSION_MASK))
return;

if (unlikely(lockdep_hardirqs_enabled())) {
@@ -3682,9 +3687,11 @@ void lockdep_hardirqs_on_prepare(unsigne

current->hardirq_chain_key = current->curr_chain_key;

- current->lockdep_recursion++;
- __trace_hardirqs_on_caller();
- lockdep_recursion_finish();
+ if (!in_nmi()) {
+ current->lockdep_recursion++;
+ __trace_hardirqs_on_caller();
+ lockdep_recursion_finish();
+ }
}
EXPORT_SYMBOL_GPL(lockdep_hardirqs_on_prepare);

@@ -3692,7 +3699,7 @@ void noinstr lockdep_hardirqs_on(unsigne
{
struct task_struct *curr = current;

- if (unlikely(!debug_locks || curr->lockdep_recursion))
+ if (DEBUG_LOCKS_WARN_ON(curr->lockdep_recursion & LOCKDEP_RECURSION_MASK))
return;

if (lockdep_hardirqs_enabled()) {
@@ -3735,8 +3742,10 @@ void noinstr lockdep_hardirqs_off(unsign
{
struct task_struct *curr = current;

- if (unlikely(!debug_locks || curr->lockdep_recursion))
- return;
+ /*
+ * Can't test recursion; NMIs can happen while in lockdep.
+ * Harmless though; all we do is clear hardirqs_enabled.
+ */

/*
* So we're supposed to get called after you mask local IRQs, but for

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