From: Waiman Long <longman@redhat.com>
To: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will.deacon@arm.com>
Cc: linux-kernel@vger.kernel.org, Waiman Long <longman@redhat.com>
Subject: [PATCH 2/5] locking/lockdep: Eliminate redundant irqs check in __lock_acquire()
Date: Fri, 28 Sep 2018 13:53:18 -0400 [thread overview]
Message-ID: <1538157201-29173-3-git-send-email-longman@redhat.com> (raw)
In-Reply-To: <1538157201-29173-1-git-send-email-longman@redhat.com>
The static __lock_acquire() function has only two callers:
1) lock_acquire()
2) reacquire_held_locks()
In lock_acquire(), raw_local_irq_save() is called before hand. So
irqs must have been disabled. So the check
DEBUG_LOCKS_WARN_ON(!irqs_disabled())
is kind of redundant in thise case. So move the above check
to reacquire_held_locks() to eliminate redundant code in the
lock_acquire path.
Signed-off-by: Waiman Long <longman@redhat.com>
---
kernel/locking/lockdep.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 8f9de7c..add0468 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3192,6 +3192,10 @@ void lockdep_init_map(struct lockdep_map *lock, const char *name,
/*
* This gets called for every mutex_lock*()/spin_lock*() operation.
* We maintain the dependency maps and validate the locking attempt:
+ *
+ * The callers must make sure that IRQs are disabled before calling it.
+ * otherwise we could get an interrupt which would want to take locks,
+ * which would end up in lockdep again.
*/
static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
int trylock, int read, int check, int hardirqs_off,
@@ -3209,14 +3213,6 @@ static int __lock_acquire(struct lockdep_map *lock, unsigned int subclass,
if (unlikely(!debug_locks))
return 0;
- /*
- * Lockdep should run with IRQs disabled, otherwise we could
- * get an interrupt which would want to take locks, which would
- * end up in lockdep and have you got a head-ache already?
- */
- if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
- return 0;
-
if (!prove_locking || lock->key == &__lockdep_no_validate__)
check = 0;
@@ -3473,6 +3469,9 @@ static int reacquire_held_locks(struct task_struct *curr, unsigned int depth,
{
struct held_lock *hlock;
+ if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
+ return 0;
+
for (hlock = curr->held_locks + idx; idx < depth; idx++, hlock++) {
if (!__lock_acquire(hlock->instance,
hlock_class(hlock)->subclass,
--
1.8.3.1
next prev parent reply other threads:[~2018-09-28 17:53 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-28 17:53 [PATCH 0/5] locking/lockdep: Improve lockdep performance Waiman Long
2018-09-28 17:53 ` [PATCH 1/5] locking/lockdep: Remove add_chain_cache_classes() Waiman Long
2018-09-28 17:53 ` Waiman Long [this message]
2018-10-02 9:06 ` [PATCH 2/5] locking/lockdep: Eliminate redundant irqs check in __lock_acquire() Ingo Molnar
2018-09-28 17:53 ` [PATCH 3/5] locking/lockdep: Add a faster path in __lock_release() Waiman Long
2018-10-02 9:03 ` Ingo Molnar
2018-09-28 17:53 ` [PATCH 4/5] locking/lockdep: Make class->ops a percpu counter Waiman Long
2018-09-28 20:25 ` kbuild test robot
2018-09-28 20:31 ` Waiman Long
2018-09-28 20:42 ` kbuild test robot
2018-10-02 9:39 ` Peter Zijlstra
2018-10-02 9:55 ` Ingo Molnar
2018-10-02 14:10 ` Waiman Long
2018-10-02 14:28 ` Peter Zijlstra
2018-10-02 18:53 ` Ingo Molnar
2018-09-28 17:53 ` [PATCH 5/5] locking/lockdep: Call lock_release after releasing the lock Waiman Long
2018-10-02 9:08 ` Ingo Molnar
2018-10-02 9:06 ` [PATCH 0/5] locking/lockdep: Improve lockdep performance Ingo Molnar
2018-10-02 13:57 ` Waiman Long
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