linux-kernel - [PATCH 2/2] lglock: update lockdep annotations to report recursive local locks

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Message-Id: <1362449845-7492-3-git-send-email-walken@google.com>
Date:	Mon,  4 Mar 2013 18:17:25 -0800
From:	Michel Lespinasse <walken@...gle.com>
To:	linux-kernel@...r.kernel.org,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>,
	Lai Jiangshan <laijs@...fujitsu.com>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	paulmck@...ux.vnet.ibm.com, Rusty Russell <rusty@...tcorp.com.au>,
	rostedt@...dmis.org, tglx@...utronix.de,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH 2/2] lglock: update lockdep annotations to report recursive local locks

Oleg Nesterov recently noticed that the lockdep annotations in lglock.c
are not sufficient to detect some obvious deadlocks, such as
lg_local_lock(LOCK) + lg_local_lock(LOCK) or
spin_lock(X) + lg_local_lock(Y) vs lg_local_lock(Y) + spin_lock(X).

Both issues are easily fixed by indicating to lockdep that lglock's local
locks are not recursive. We shouldn't use the rwlock acquire/release
functions here, as lglock doesn't share the same semantics. Instead
we can base our lockdep annotations on the lock_acquire_shared
(for local lglock) and lock_acquire_exclusive (for global lglock)
helpers.

I am not proposing new lglock specific helpers as I don't see the point
of the existing second level of helpers :)

Signed-off-by: Michel Lespinasse <walken@...gle.com>

---
 kernel/lglock.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/kernel/lglock.c b/kernel/lglock.c
index 6535a667a5a7..86ae2aebf004 100644
--- a/kernel/lglock.c
+++ b/kernel/lglock.c
@@ -21,7 +21,7 @@ void lg_local_lock(struct lglock *lg)
 	arch_spinlock_t *lock;
 
 	preempt_disable();
-	rwlock_acquire_read(&lg->lock_dep_map, 0, 0, _RET_IP_);
+	lock_acquire_shared(&lg->lock_dep_map, 0, 0, NULL, _RET_IP_);
 	lock = this_cpu_ptr(lg->lock);
 	arch_spin_lock(lock);
 }
@@ -31,7 +31,7 @@ void lg_local_unlock(struct lglock *lg)
 {
 	arch_spinlock_t *lock;
 
-	rwlock_release(&lg->lock_dep_map, 1, _RET_IP_);
+	lock_release(&lg->lock_dep_map, 1, _RET_IP_);
 	lock = this_cpu_ptr(lg->lock);
 	arch_spin_unlock(lock);
 	preempt_enable();
@@ -43,7 +43,7 @@ void lg_local_lock_cpu(struct lglock *lg, int cpu)
 	arch_spinlock_t *lock;
 
 	preempt_disable();
-	rwlock_acquire_read(&lg->lock_dep_map, 0, 0, _RET_IP_);
+	lock_acquire_shared(&lg->lock_dep_map, 0, 0, NULL, _RET_IP_);
 	lock = per_cpu_ptr(lg->lock, cpu);
 	arch_spin_lock(lock);
 }
@@ -53,7 +53,7 @@ void lg_local_unlock_cpu(struct lglock *lg, int cpu)
 {
 	arch_spinlock_t *lock;
 
-	rwlock_release(&lg->lock_dep_map, 1, _RET_IP_);
+	lock_release(&lg->lock_dep_map, 1, _RET_IP_);
 	lock = per_cpu_ptr(lg->lock, cpu);
 	arch_spin_unlock(lock);
 	preempt_enable();
@@ -65,7 +65,7 @@ void lg_global_lock(struct lglock *lg)
 	int i;
 
 	preempt_disable();
-	rwlock_acquire(&lg->lock_dep_map, 0, 0, _RET_IP_);
+	lock_acquire_exclusive(&lg->lock_dep_map, 0, 0, NULL, _RET_IP_);
 	for_each_possible_cpu(i) {
 		arch_spinlock_t *lock;
 		lock = per_cpu_ptr(lg->lock, i);
@@ -78,7 +78,7 @@ void lg_global_unlock(struct lglock *lg)
 {
 	int i;
 
-	rwlock_release(&lg->lock_dep_map, 1, _RET_IP_);
+	lock_release(&lg->lock_dep_map, 1, _RET_IP_);
 	for_each_possible_cpu(i) {
 		arch_spinlock_t *lock;
 		lock = per_cpu_ptr(lg->lock, i);
-- 
1.8.1.3
--
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