kernel/locking/lockdep.c: convert hash tables to hlists

Mike said:

: CONFIG_UBSAN_ALIGNMENT breaks x86-64 kernel with lockdep enabled, i.  e
: kernel with CONFIG_UBSAN_ALIGNMENT fails to load without even any error
: message.
:
: The problem is that ubsan callbacks use spinlocks and might be called
: before lockdep is initialized.  Particularly this line in the
: reserve_ebda_region function causes problem:
:
: lowmem = *(unsigned short *)__va(BIOS_LOWMEM_KILOBYTES);
:
: If i put lockdep_init() before reserve_ebda_region call in
: x86_64_start_reservations kernel loads well.

Fix this ordering issue permanently: change lockdep so that it uses
hlists for the hash tables.  Unlike a list_head, an hlist_head is in its
initialized state when it is all-zeroes, so lockdep is ready for
operation immediately upon boot - lockdep_init() need not have run.

The patch will also save some memory.

lockdep_init() and lockdep_initialized can be done away with now - a 4.6
patch has been prepared to do this.

Reported-by: Mike Krinkin <krinkin.m.u@gmail.com>
Suggested-by: Mike Krinkin <krinkin.m.u@gmail.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 19 insertions, 23 deletions

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 60ace56618f6..7537e568dabe 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -292,7 +292,7 @@ LIST_HEAD(all_lock_classes);
 #define __classhashfn(key)      hash_long((unsigned long)key, CLASSHASH_BITS)
 #define classhashentry(key)     (classhash_table + __classhashfn((key)))
 
-static struct list_head classhash_table[CLASSHASH_SIZE];
+static struct hlist_head classhash_table[CLASSHASH_SIZE];
 
 /*
  * We put the lock dependency chains into a hash-table as well, to cache
@@ -303,7 +303,7 @@ static struct list_head classhash_table[CLASSHASH_SIZE];
 #define __chainhashfn(chain)    hash_long(chain, CHAINHASH_BITS)
 #define chainhashentry(chain)   (chainhash_table + __chainhashfn((chain)))
 
-static struct list_head chainhash_table[CHAINHASH_SIZE];
+static struct hlist_head chainhash_table[CHAINHASH_SIZE];
 
 /*
  * The hash key of the lock dependency chains is a hash itself too:
@@ -666,7 +666,7 @@ static inline struct lock_class *
 look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
 {
         struct lockdep_subclass_key *key;
-        struct list_head *hash_head;
+        struct hlist_head *hash_head;
         struct lock_class *class;
 
 #ifdef CONFIG_DEBUG_LOCKDEP
@@ -719,7 +719,7 @@ look_up_lock_class(struct lockdep_map *lock, unsigned int subclass)
         if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
                 return NULL;
 
-        list_for_each_entry_rcu(class, hash_head, hash_entry) {
+        hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
                 if (class->key == key) {
                         /*
                          * Huh! same key, different name? Did someone trample
@@ -742,7 +742,7 @@ static inline struct lock_class *
 register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
 {
         struct lockdep_subclass_key *key;
-        struct list_head *hash_head;
+        struct hlist_head *hash_head;
         struct lock_class *class;
 
         DEBUG_LOCKS_WARN_ON(!irqs_disabled());
@@ -774,7 +774,7 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
          * We have to do the hash-walk again, to avoid races
          * with another CPU:
          */
-        list_for_each_entry_rcu(class, hash_head, hash_entry) {
+        hlist_for_each_entry_rcu(class, hash_head, hash_entry) {
                 if (class->key == key)
                         goto out_unlock_set;
         }
@@ -805,7 +805,7 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force)
          * We use RCU's safe list-add method to make
          * parallel walking of the hash-list safe:
          */
-        list_add_tail_rcu(&class->hash_entry, hash_head);
+        hlist_add_head_rcu(&class->hash_entry, hash_head);
         /*
          * Add it to the global list of classes:
          */
@@ -2017,7 +2017,7 @@ static inline int lookup_chain_cache(struct task_struct *curr,
                                      u64 chain_key)
 {
         struct lock_class *class = hlock_class(hlock);
-        struct list_head *hash_head = chainhashentry(chain_key);
+        struct hlist_head *hash_head = chainhashentry(chain_key);
         struct lock_chain *chain;
         struct held_lock *hlock_curr;
         int i, j;
@@ -2033,7 +2033,7 @@ static inline int lookup_chain_cache(struct task_struct *curr,
          * We can walk it lock-free, because entries only get added
          * to the hash:
          */
-        list_for_each_entry_rcu(chain, hash_head, entry) {
+        hlist_for_each_entry_rcu(chain, hash_head, entry) {
                 if (chain->chain_key == chain_key) {
 cache_hit:
                         debug_atomic_inc(chain_lookup_hits);
@@ -2057,7 +2057,7 @@ cache_hit:
         /*
          * We have to walk the chain again locked - to avoid duplicates:
          */
-        list_for_each_entry(chain, hash_head, entry) {
+        hlist_for_each_entry(chain, hash_head, entry) {
                 if (chain->chain_key == chain_key) {
                         graph_unlock();
                         goto cache_hit;
@@ -2091,7 +2091,7 @@ cache_hit:
                 }
                 chain_hlocks[chain->base + j] = class - lock_classes;
         }
-        list_add_tail_rcu(&chain->entry, hash_head);
+        hlist_add_head_rcu(&chain->entry, hash_head);
         debug_atomic_inc(chain_lookup_misses);
         inc_chains();
 
@@ -3875,7 +3875,7 @@ void lockdep_reset(void)
         nr_process_chains = 0;
         debug_locks = 1;
         for (i = 0; i < CHAINHASH_SIZE; i++)
-                INIT_LIST_HEAD(chainhash_table + i);
+                INIT_HLIST_HEAD(chainhash_table + i);
         raw_local_irq_restore(flags);
 }
 
@@ -3894,7 +3894,7 @@ static void zap_class(struct lock_class *class)
         /*
          * Unhash the class and remove it from the all_lock_classes list:
          */
-        list_del_rcu(&class->hash_entry);
+        hlist_del_rcu(&class->hash_entry);
         list_del_rcu(&class->lock_entry);
 
         RCU_INIT_POINTER(class->key, NULL);
@@ -3917,7 +3917,7 @@ static inline int within(const void *addr, void *start, unsigned long size)
 void lockdep_free_key_range(void *start, unsigned long size)
 {
         struct lock_class *class;
-        struct list_head *head;
+        struct hlist_head *head;
         unsigned long flags;
         int i;
         int locked;
@@ -3930,9 +3930,7 @@ void lockdep_free_key_range(void *start, unsigned long size)
          */
         for (i = 0; i < CLASSHASH_SIZE; i++) {
                 head = classhash_table + i;
-                if (list_empty(head))
-                        continue;
-                list_for_each_entry_rcu(class, head, hash_entry) {
+                hlist_for_each_entry_rcu(class, head, hash_entry) {
                         if (within(class->key, start, size))
                                 zap_class(class);
                         else if (within(class->name, start, size))
@@ -3962,7 +3960,7 @@ void lockdep_free_key_range(void *start, unsigned long size)
 void lockdep_reset_lock(struct lockdep_map *lock)
 {
         struct lock_class *class;
-        struct list_head *head;
+        struct hlist_head *head;
         unsigned long flags;
         int i, j;
         int locked;
@@ -3987,9 +3985,7 @@ void lockdep_reset_lock(struct lockdep_map *lock)
         locked = graph_lock();
         for (i = 0; i < CLASSHASH_SIZE; i++) {
                 head = classhash_table + i;
-                if (list_empty(head))
-                        continue;
-                list_for_each_entry_rcu(class, head, hash_entry) {
+                hlist_for_each_entry_rcu(class, head, hash_entry) {
                         int match = 0;
 
                         for (j = 0; j < NR_LOCKDEP_CACHING_CLASSES; j++)
@@ -4027,10 +4023,10 @@ void lockdep_init(void)
                 return;
 
         for (i = 0; i < CLASSHASH_SIZE; i++)
-                INIT_LIST_HEAD(classhash_table + i);
+                INIT_HLIST_HEAD(classhash_table + i);
 
         for (i = 0; i < CHAINHASH_SIZE; i++)
-                INIT_LIST_HEAD(chainhash_table + i);
+                INIT_HLIST_HEAD(chainhash_table + i);
 
         lockdep_initialized = 1;
 }