From: Bart Van Assche <bvanassche@acm.org>
To: peterz@infradead.org
Cc: mingo@redhat.com, tj@kernel.org, longman@redhat.com,
johannes.berg@intel.com, linux-kernel@vger.kernel.org,
Bart Van Assche <bvanassche@acm.org>,
Johannes Berg <johannes@sipsolutions.net>
Subject: [PATCH v6 11/16] locking/lockdep: Reuse lock chains that have been freed
Date: Wed, 9 Jan 2019 13:01:59 -0800 [thread overview]
Message-ID: <20190109210204.192109-12-bvanassche@acm.org> (raw)
In-Reply-To: <20190109210204.192109-1-bvanassche@acm.org>
A previous patch introduced a lock chain leak. Fix that leak by reusing
lock chains that have been freed.
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Waiman Long <longman@redhat.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
---
kernel/locking/lockdep.c | 62 ++++++++++++++++++++++------------------
1 file changed, 34 insertions(+), 28 deletions(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index ef3809e21fa9..a8ea03bfc944 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -299,6 +299,7 @@ static struct pending_free {
struct rcu_head rcu_head;
bool scheduled;
DECLARE_BITMAP(list_entries_being_freed, MAX_LOCKDEP_ENTRIES);
+ DECLARE_BITMAP(lock_chains_being_freed, MAX_LOCKDEP_CHAINS);
} pending_free[2];
static DECLARE_WAIT_QUEUE_HEAD(rcu_cb);
@@ -2110,8 +2111,8 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next)
return 0;
}
-static unsigned long nr_lock_chains;
struct lock_chain lock_chains[MAX_LOCKDEP_CHAINS];
+static DECLARE_BITMAP(lock_chains_in_use, MAX_LOCKDEP_CHAINS);
int nr_chain_hlocks;
static u16 chain_hlocks[MAX_LOCKDEP_CHAIN_HLOCKS];
@@ -2250,12 +2251,25 @@ static int check_no_collision(struct task_struct *curr,
*/
long lockdep_next_lockchain(long i)
{
- return i + 1 < nr_lock_chains ? i + 1 : -2;
+ i = find_next_bit(lock_chains_in_use, ARRAY_SIZE(lock_chains), i + 1);
+ return i < ARRAY_SIZE(lock_chains) ? i : -2;
}
unsigned long lock_chain_count(void)
{
- return nr_lock_chains;
+ return bitmap_weight(lock_chains_in_use, ARRAY_SIZE(lock_chains));
+}
+
+/* Must be called with the graph lock held. */
+static struct lock_chain *alloc_lock_chain(void)
+{
+ int idx = find_first_zero_bit(lock_chains_in_use,
+ ARRAY_SIZE(lock_chains));
+
+ if (unlikely(idx >= ARRAY_SIZE(lock_chains)))
+ return NULL;
+ __set_bit(idx, lock_chains_in_use);
+ return lock_chains + idx;
}
/*
@@ -2274,20 +2288,8 @@ static inline int add_chain_cache(struct task_struct *curr,
struct lock_chain *chain;
int i, j;
- /*
- * Allocate a new chain entry from the static array, and add
- * it to the hash:
- */
-
- /*
- * We might need to take the graph lock, ensure we've got IRQs
- * disabled to make this an IRQ-safe lock.. for recursion reasons
- * lockdep won't complain about its own locking errors.
- */
- if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
- return 0;
-
- if (unlikely(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
+ chain = alloc_lock_chain();
+ if (!chain) {
if (!debug_locks_off_graph_unlock())
return 0;
@@ -2295,7 +2297,6 @@ static inline int add_chain_cache(struct task_struct *curr,
dump_stack();
return 0;
}
- chain = lock_chains + nr_lock_chains++;
chain->chain_key = chain_key;
chain->irq_context = hlock->irq_context;
i = get_first_held_lock(curr, hlock);
@@ -4223,7 +4224,8 @@ void lockdep_reset(void)
}
/* Remove a class from a lock chain. Must be called with the graph lock held. */
-static void remove_class_from_lock_chain(struct lock_chain *chain,
+static void remove_class_from_lock_chain(struct pending_free *pf,
+ struct lock_chain *chain,
struct lock_class *class)
{
#ifdef CONFIG_PROVE_LOCKING
@@ -4261,6 +4263,7 @@ static void remove_class_from_lock_chain(struct lock_chain *chain,
* hlist_for_each_entry_rcu() loop is safe.
*/
hlist_del_rcu(&chain->entry);
+ __set_bit(chain - lock_chains, pf->lock_chains_being_freed);
if (chain->depth == 0)
return;
/*
@@ -4269,22 +4272,19 @@ static void remove_class_from_lock_chain(struct lock_chain *chain,
*/
if (lookup_chain_cache(chain_key))
return;
- if (WARN_ON_ONCE(nr_lock_chains >= MAX_LOCKDEP_CHAINS)) {
+ new_chain = alloc_lock_chain();
+ if (WARN_ON_ONCE(!new_chain)) {
debug_locks_off();
return;
}
- /*
- * Leak *chain because it is not safe to reinsert it before an RCU
- * grace period has expired.
- */
- new_chain = lock_chains + nr_lock_chains++;
*new_chain = *chain;
hlist_add_head_rcu(&new_chain->entry, chainhashentry(chain_key));
#endif
}
/* Must be called with the graph lock held. */
-static void remove_class_from_lock_chains(struct lock_class *class)
+static void remove_class_from_lock_chains(struct pending_free *pf,
+ struct lock_class *class)
{
struct lock_chain *chain;
struct hlist_head *head;
@@ -4293,7 +4293,7 @@ static void remove_class_from_lock_chains(struct lock_class *class)
for (i = 0; i < ARRAY_SIZE(chainhash_table); i++) {
head = chainhash_table + i;
hlist_for_each_entry_rcu(chain, head, entry) {
- remove_class_from_lock_chain(chain, class);
+ remove_class_from_lock_chain(pf, chain, class);
}
}
}
@@ -4334,7 +4334,7 @@ static void zap_class(struct pending_free *pf, struct lock_class *class)
class->name);
}
- remove_class_from_lock_chains(class);
+ remove_class_from_lock_chains(pf, class);
}
static void reinit_class(struct lock_class *class)
@@ -4383,6 +4383,11 @@ static void free_zapped_classes(struct rcu_head *ch)
bitmap_andnot(list_entries_in_use, list_entries_in_use,
pf->list_entries_being_freed, ARRAY_SIZE(list_entries));
bitmap_clear(pf->list_entries_being_freed, 0, ARRAY_SIZE(list_entries));
+#ifdef CONFIG_PROVE_LOCKING
+ bitmap_andnot(lock_chains_in_use, lock_chains_in_use,
+ pf->lock_chains_being_freed, ARRAY_SIZE(lock_chains));
+ bitmap_clear(pf->lock_chains_being_freed, 0, ARRAY_SIZE(lock_chains));
+#endif
graph_unlock();
restore_irqs:
raw_local_irq_restore(flags);
@@ -4675,6 +4680,7 @@ void __init lockdep_init(void)
#ifdef CONFIG_PROVE_LOCKING
+ sizeof(lock_cq)
+ sizeof(lock_chains)
+ + sizeof(lock_chains_in_use)
+ sizeof(chain_hlocks)
#endif
) / 1024
--
2.20.1.97.g81188d93c3-goog
next prev parent reply other threads:[~2019-01-09 21:04 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-09 21:01 [PATCH v6 00/16] locking/lockdep: Add support for dynamic keys Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 01/16] locking/lockdep: Fix reported required memory size Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 02/16] locking/lockdep: Avoid that add_chain_cache() adds an invalid chain to the cache Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 03/16] locking/lockdep: Make zap_class() remove all matching lock order entries Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 04/16] locking/lockdep: Reorder struct lock_class members Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 05/16] locking/lockdep: Initialize the locks_before and locks_after lists earlier Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 06/16] locking/lockdep: Split lockdep_free_key_range() and lockdep_reset_lock() Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 07/16] locking/lockdep: Make it easy to detect whether or not inside a selftest Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 08/16] locking/lockdep: Free lock classes that are no longer in use Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 09/16] locking/lockdep: Reuse list entries " Bart Van Assche
2019-01-09 21:01 ` [PATCH v6 10/16] locking/lockdep: Introduce lockdep_next_lockchain() and lock_chain_count() Bart Van Assche
2019-01-09 21:01 ` Bart Van Assche [this message]
2019-01-09 21:02 ` [PATCH v6 12/16] locking/lockdep: Check data structure consistency Bart Van Assche
2019-01-09 21:02 ` [PATCH v6 13/16] locking/lockdep: Verify whether lock objects are small enough to be used as class keys Bart Van Assche
2019-01-09 21:02 ` [PATCH v6 14/16] locking/lockdep: Add support for dynamic keys Bart Van Assche
2019-01-09 21:02 ` [PATCH v6 15/16] kernel/workqueue: Use dynamic lockdep keys for workqueues Bart Van Assche
2019-01-09 21:02 ` [PATCH v6 16/16] lockdep tests: Test dynamic key registration Bart Van Assche
2019-01-11 12:48 ` [PATCH v6 00/16] locking/lockdep: Add support for dynamic keys Peter Zijlstra
2019-01-11 15:55 ` Bart Van Assche
2019-01-11 16:55 ` Peter Zijlstra
2019-01-11 17:01 ` Bart Van Assche
2019-01-14 12:52 ` Peter Zijlstra
2019-01-14 16:52 ` Bart Van Assche
2019-01-18 9:48 ` Peter Zijlstra
2019-01-19 2:34 ` Bart Van Assche
2019-02-01 12:15 ` Peter Zijlstra
2019-02-03 17:36 ` Bart Van Assche
2019-02-08 11:43 ` Will Deacon
2019-02-08 16:31 ` Bart Van Assche
2019-02-13 22:32 ` Bart Van Assche
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