On 2/1/21 1:09 PM, Dmitry Vyukov wrote:
On Mon, Feb 1, 2021 at 6:54 PM Waiman Long <longman@xxxxxxxxxx> wrote:
On 2/1/21 6:23 AM, Peter Zijlstra wrote:
On Mon, Feb 01, 2021 at 10:50:58AM +0100, Peter Zijlstra wrote:
queued_spin_unlock arch/x86/include/asm/qspinlock.h:56 [inline]
lockdep_unlock+0x10e/0x290 kernel/locking/lockdep.c:124
debug_locks_off_graph_unlock kernel/locking/lockdep.c:165 [inline]
print_usage_bug kernel/locking/lockdep.c:3710 [inline]
Ha, I think you hit a bug in lockdep.
Something like so I suppose.
---
Subject: locking/lockdep: Avoid unmatched unlock
From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Mon Feb 1 11:55:38 CET 2021
Commit f6f48e180404 ("lockdep: Teach lockdep about "USED" <- "IN-NMI"
inversions") overlooked that print_usage_bug() releases the graph_lock
and called it without the graph lock held.
Fixes: f6f48e180404 ("lockdep: Teach lockdep about "USED" <- "IN-NMI" inversions")
Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
---
kernel/locking/lockdep.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3773,7 +3773,7 @@ static void
print_usage_bug(struct task_struct *curr, struct held_lock *this,
enum lock_usage_bit prev_bit, enum lock_usage_bit new_bit)
{
- if (!debug_locks_off_graph_unlock() || debug_locks_silent)
+ if (!debug_locks_off() || debug_locks_silent)
return;
pr_warn("\n");
@@ -3814,6 +3814,7 @@ valid_state(struct task_struct *curr, st
enum lock_usage_bit new_bit, enum lock_usage_bit bad_bit)
{
if (unlikely(hlock_class(this)->usage_mask & (1 << bad_bit))) {
+ graph_unlock()
print_usage_bug(curr, this, bad_bit, new_bit);
return 0;
}
I have also suspected doing unlock without a corresponding lock. This
patch looks good to me.
Acked-by: Waiman Long <longman@xxxxxxxxxx>
Just so that it's not lost: there is still a bug related to bpf map lock, right?
That is right. This patch just fixes the bug in lockdep.
Cheers,
Longman
