linux-kernel - Re: unpinning an unpinned lock

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Message-ID: <20150916141040.GA11639@twins.programming.kicks-ass.net>
Date:	Wed, 16 Sep 2015 16:10:40 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Tim Spriggs <tspriggs@...le.com>, davej@...emonkey.org.uk,
	sasha.levin@...cle.com, linux-kernel@...r.kernel.org
Subject: Re: unpinning an unpinned lock

On Wed, Sep 16, 2015 at 12:55:35PM +0200, Peter Zijlstra wrote:

> In any case, I'll have another go at tackling this, otherwise I'll have
> to disable this warning for now.
> 
> Note that this lockdep 'feature' is pure annotation, no actual logic was
> changed.

Sasha, can you give this a spin?

So there's 2 places where we take a lock out of the middle of a stack,
and in those cases it would fail to preserve the pin_count.

---
 kernel/locking/lockdep.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 8acfbf773e06..4e49cc4c9952 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3068,7 +3068,7 @@ static int __lock_is_held(struct lockdep_map *lock);
 static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 			  int trylock, int read, int check, int hardirqs_off,
 			  struct lockdep_map *nest_lock, unsigned long ip,
-			  int references)
+			  int references, int pin_count)
 {
 	struct task_struct *curr = current;
 	struct lock_class *class = NULL;
@@ -3157,7 +3157,7 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 	hlock->waittime_stamp = 0;
 	hlock->holdtime_stamp = lockstat_clock();
 #endif
-	hlock->pin_count = 0;
+	hlock->pin_count = pin_count;
 
 	if (check && !mark_irqflags(curr, hlock))
 		return 0;
@@ -3343,7 +3343,7 @@ __lock_set_class(struct lockdep_map *lock, const char *name,
 			hlock_class(hlock)->subclass, hlock->trylock,
 				hlock->read, hlock->check, hlock->hardirqs_off,
 				hlock->nest_lock, hlock->acquire_ip,
-				hlock->references))
+				hlock->references, hlock->pin_count))
 			return 0;
 	}
 
@@ -3433,7 +3433,7 @@ __lock_release(struct lockdep_map *lock, int nested, unsigned long ip)
 			hlock_class(hlock)->subclass, hlock->trylock,
 				hlock->read, hlock->check, hlock->hardirqs_off,
 				hlock->nest_lock, hlock->acquire_ip,
-				hlock->references))
+				hlock->references, hlock->pin_count))
 			return 0;
 	}
 
@@ -3583,7 +3583,7 @@ void lock_acquire(struct lockdep_map *lock, unsigned int subclass,
 	current->lockdep_recursion = 1;
 	trace_lock_acquire(lock, subclass, trylock, read, check, nest_lock, ip);
 	__lock_acquire(lock, subclass, trylock, read, check,
-		       irqs_disabled_flags(flags), nest_lock, ip, 0);
+		       irqs_disabled_flags(flags), nest_lock, ip, 0, 0);
 	current->lockdep_recursion = 0;
 	raw_local_irq_restore(flags);
 }
--
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