linux-kernel - [PATCH] lockdep: Do no validate wait context for novalidate class

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Date:   Mon, 29 Jun 2020 22:15:29 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        tglx@...utronix.de,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH] lockdep: Do no validate wait context for novalidate class

The novalidate class is ignored in the lockchain validation but is
considered in the wait context validation.
If a mutex and a spinlock_t is ignored by using
lockdep_set_novalidate_class() then both locks will share the same lock
class. From the wait validation point of view the mutex will then appear
like a spinlock_t and the validator will complain if another mutex will
be acquired.

Ignore the nonvalidate locks from wait context checking.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 kernel/locking/lockdep.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 29a8de4c50b90..fb9a642d8ebef 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -4067,7 +4067,7 @@ static int check_wait_context(struct task_struct *curr, struct held_lock *next)
 	 */
 	for (depth = curr->lockdep_depth - 1; depth >= 0; depth--) {
 		struct held_lock *prev = curr->held_locks + depth;
-		if (prev->irq_context != next->irq_context)
+		if (prev->check && prev->irq_context != next->irq_context)
 			break;
 	}
 	depth++;
@@ -4078,6 +4078,9 @@ static int check_wait_context(struct task_struct *curr, struct held_lock *next)
 		struct held_lock *prev = curr->held_locks + depth;
 		short prev_inner = hlock_class(prev)->wait_type_inner;
 
+		if (!prev->check)
+			continue;
+
 		if (prev_inner) {
 			/*
 			 * We can have a bigger inner than a previous one
-- 
2.27.0