* [PATCH] locking/lockdep: Make lockdep_register_key() ignore 'debug_locks'
@ 2019-04-11 17:26 Bart Van Assche
2019-04-12 5:47 ` Ingo Molnar
0 siblings, 1 reply; 4+ messages in thread
From: Bart Van Assche @ 2019-04-11 17:26 UTC (permalink / raw)
To: Peter Zijlstra
Cc: Ingo Molnar, Thomas Gleixner, linux-kernel, Bart Van Assche,
Will Deacon, Waiman Long, shenghui
If lockdep_register_key() and lockdep_unregister_key() are called with
debug_locks == false then the following warning is reported:
WARNING: CPU: 2 PID: 15145 at kernel/locking/lockdep.c:4920 lockdep_unregister_key+0x1ad/0x240
That warning is reported because lockdep_unregister_key() ignores the
value of 'debug_locks' and because the behavior of lockdep_register_key()
depends on whether or not 'debug_locks' is set. Fix this inconsistency
by making lockdep_register_key() unconditionally register lock keys.
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Waiman Long <longman@redhat.com>
Cc: shenghui <shhuiw@foxmail.com>
Reported-by: shenghui <shhuiw@foxmail.com>
Fixes: a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer in use") # v5.1-rc1.
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
kernel/locking/lockdep.c | 7 ++++---
1 file changed, 4 insertions(+), 3 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index d2d65bbfae01..a228509b62f1 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1027,15 +1027,16 @@ void lockdep_register_key(struct lock_class_key *key)
hash_head = keyhashentry(key);
raw_local_irq_save(flags);
- if (!graph_lock())
- goto restore_irqs;
+ arch_spin_lock(&lockdep_lock);
+ current->lockdep_recursion = 1;
hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
if (WARN_ON_ONCE(k == key))
goto out_unlock;
}
hlist_add_head_rcu(&key->hash_entry, hash_head);
out_unlock:
- graph_unlock();
+ current->lockdep_recursion = 0;
+ arch_spin_unlock(&lockdep_lock);
restore_irqs:
raw_local_irq_restore(flags);
}
--
2.21.0.196.g041f5ea1cf98
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] locking/lockdep: Make lockdep_register_key() ignore 'debug_locks'
2019-04-11 17:26 [PATCH] locking/lockdep: Make lockdep_register_key() ignore 'debug_locks' Bart Van Assche
@ 2019-04-12 5:47 ` Ingo Molnar
2019-04-12 15:32 ` Bart Van Assche
0 siblings, 1 reply; 4+ messages in thread
From: Ingo Molnar @ 2019-04-12 5:47 UTC (permalink / raw)
To: Bart Van Assche
Cc: Peter Zijlstra, Ingo Molnar, Thomas Gleixner, linux-kernel,
Will Deacon, Waiman Long, shenghui
* Bart Van Assche <bvanassche@acm.org> wrote:
> If lockdep_register_key() and lockdep_unregister_key() are called with
> debug_locks == false then the following warning is reported:
>
> WARNING: CPU: 2 PID: 15145 at kernel/locking/lockdep.c:4920 lockdep_unregister_key+0x1ad/0x240
>
> That warning is reported because lockdep_unregister_key() ignores the
> value of 'debug_locks' and because the behavior of lockdep_register_key()
> depends on whether or not 'debug_locks' is set. Fix this inconsistency
> by making lockdep_register_key() unconditionally register lock keys.
>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Waiman Long <longman@redhat.com>
> Cc: shenghui <shhuiw@foxmail.com>
> Reported-by: shenghui <shhuiw@foxmail.com>
> Fixes: a0b0fd53e1e6 ("locking/lockdep: Free lock classes that are no longer in use") # v5.1-rc1.
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
> kernel/locking/lockdep.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> index d2d65bbfae01..a228509b62f1 100644
> --- a/kernel/locking/lockdep.c
> +++ b/kernel/locking/lockdep.c
> @@ -1027,15 +1027,16 @@ void lockdep_register_key(struct lock_class_key *key)
> hash_head = keyhashentry(key);
>
> raw_local_irq_save(flags);
> - if (!graph_lock())
> - goto restore_irqs;
> + arch_spin_lock(&lockdep_lock);
> + current->lockdep_recursion = 1;
> hlist_for_each_entry_rcu(k, hash_head, hash_entry) {
> if (WARN_ON_ONCE(k == key))
> goto out_unlock;
> }
> hlist_add_head_rcu(&key->hash_entry, hash_head);
> out_unlock:
> - graph_unlock();
> + current->lockdep_recursion = 0;
> + arch_spin_unlock(&lockdep_lock);
> restore_irqs:
> raw_local_irq_restore(flags);
> }
So why don't we add a debug_locks test to lockdep_unregister_key()
instead? The general principle to bring lockdep to a screeching halt when
bugs are detected, ASAP.
Thanks,
Ingo
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] locking/lockdep: Make lockdep_register_key() ignore 'debug_locks'
2019-04-12 5:47 ` Ingo Molnar
@ 2019-04-12 15:32 ` Bart Van Assche
2019-04-13 8:29 ` Ingo Molnar
0 siblings, 1 reply; 4+ messages in thread
From: Bart Van Assche @ 2019-04-12 15:32 UTC (permalink / raw)
To: Ingo Molnar
Cc: Peter Zijlstra, Ingo Molnar, Thomas Gleixner, linux-kernel,
Will Deacon, Waiman Long, shenghui
On Fri, 2019-04-12 at 07:47 +0200, Ingo Molnar wrote:
> So why don't we add a debug_locks test to lockdep_unregister_key()
> instead? The general principle to bring lockdep to a screeching halt when
> bugs are detected, ASAP.
Hi Ingo,
Since this issue was introduced by patch "locking/lockdep: Zap lock classes
even with lock debugging disabled" and since that patch is in the tip tree
but not yet upstream: do you prefer that I post a version 3 of that patch or
do you rather prefer that I post a follow-up patch?
Thanks,
Bart.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] locking/lockdep: Make lockdep_register_key() ignore 'debug_locks'
2019-04-12 15:32 ` Bart Van Assche
@ 2019-04-13 8:29 ` Ingo Molnar
0 siblings, 0 replies; 4+ messages in thread
From: Ingo Molnar @ 2019-04-13 8:29 UTC (permalink / raw)
To: Bart Van Assche
Cc: Peter Zijlstra, Ingo Molnar, Thomas Gleixner, linux-kernel,
Will Deacon, Waiman Long, shenghui
* Bart Van Assche <bvanassche@acm.org> wrote:
> On Fri, 2019-04-12 at 07:47 +0200, Ingo Molnar wrote:
> > So why don't we add a debug_locks test to lockdep_unregister_key()
> > instead? The general principle to bring lockdep to a screeching halt when
> > bugs are detected, ASAP.
>
> Hi Ingo,
>
> Since this issue was introduced by patch "locking/lockdep: Zap lock classes
> even with lock debugging disabled" and since that patch is in the tip tree
> but not yet upstream: do you prefer that I post a version 3 of that patch or
> do you rather prefer that I post a follow-up patch?
The crash fix is now upstream, mind sending a followup patch for the
warning fix?
Thanks,
Ingo
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2019-04-13 8:30 UTC | newest]
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2019-04-11 17:26 [PATCH] locking/lockdep: Make lockdep_register_key() ignore 'debug_locks' Bart Van Assche
2019-04-12 5:47 ` Ingo Molnar
2019-04-12 15:32 ` Bart Van Assche
2019-04-13 8:29 ` Ingo Molnar
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