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 v2 2/5] locking/lockdep: Eliminate redundant irqs check in __lock_acquire()
Date: Tue, 2 Oct 2018 16:19:17 -0400 [thread overview]
Message-ID: <1538511560-10090-3-git-send-email-longman@redhat.com> (raw)
In-Reply-To: <1538511560-10090-1-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 beforehand. So
IRQs must have been disabled. So the check
DEBUG_LOCKS_WARN_ON(!irqs_disabled())
is kind of redundant in this 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 8f9de7cd11ab..bd59163b0550 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -3192,6 +3192,10 @@ static int __lock_is_held(const struct lockdep_map *lock, int read);
/*
* 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,
--
2.18.0
next prev parent reply other threads:[~2018-10-02 20:20 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-10-02 20:19 [PATCH v2 0/5] locking/lockdep: Improve lockdep performance Waiman Long
2018-10-02 20:19 ` [PATCH v2 1/5] locking/lockdep: Remove add_chain_cache_classes() Waiman Long
2018-10-03 7:30 ` [tip:locking/core] " tip-bot for Waiman Long
2018-10-02 20:19 ` Waiman Long [this message]
2018-10-03 7:31 ` [tip:locking/core] locking/lockdep: Eliminate redundant IRQs check in __lock_acquire() tip-bot for Waiman Long
2018-10-02 20:19 ` [PATCH v2 3/5] locking/lockdep: Add a faster path in __lock_release() Waiman Long
2018-10-03 7:31 ` [tip:locking/core] " tip-bot for Waiman Long
2018-10-02 20:19 ` [PATCH v2 4/5] locking/lockdep: Make class->ops a percpu counter Waiman Long
2018-10-03 7:48 ` Peter Zijlstra
2018-10-03 7:54 ` Ingo Molnar
2018-10-03 8:24 ` Peter Zijlstra
2018-10-03 13:57 ` Waiman Long
2018-10-03 17:07 ` Waiman Long
2018-10-04 10:14 ` Ingo Molnar
2018-10-04 13:05 ` Waiman Long
2018-10-09 10:54 ` [tip:locking/core] locking/lockdep: Make class->ops a percpu counter and move it under CONFIG_DEBUG_LOCKDEP=y tip-bot for Waiman Long
2018-10-02 20:19 ` [PATCH v2 5/5] locking/lockdep: Call lock_release() after releasing the lock Waiman Long
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