Instead of abandoning elements of list_entries[] that are no longer in use, make alloc_list_entry() reuse array elements that have been freed.
Cc: Peter Zijlstra <[email protected]> Cc: Waiman Long <[email protected]> Cc: Johannes Berg <[email protected]> Signed-off-by: Bart Van Assche <[email protected]> --- kernel/locking/lockdep.c | 33 +++++++++++++++++++++++---------- 1 file changed, 23 insertions(+), 10 deletions(-) diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 82dd7d2851eb..2da45621f741 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -45,6 +45,7 @@ #include <linux/hash.h> #include <linux/ftrace.h> #include <linux/stringify.h> +#include <linux/bitmap.h> #include <linux/bitops.h> #include <linux/gfp.h> #include <linux/random.h> @@ -132,6 +133,7 @@ static inline int debug_locks_off_graph_unlock(void) unsigned long nr_list_entries; static struct lock_list list_entries[MAX_LOCKDEP_ENTRIES]; +static DECLARE_BITMAP(list_entries_in_use, MAX_LOCKDEP_ENTRIES); /* * All data structures here are protected by the global debug_lock. @@ -296,6 +298,7 @@ static struct pending_free { struct list_head zapped_classes; struct rcu_head rcu_head; bool scheduled; + DECLARE_BITMAP(list_entries_being_freed, MAX_LOCKDEP_ENTRIES); } pending_free[2]; static DECLARE_WAIT_QUEUE_HEAD(rcu_cb); @@ -891,7 +894,10 @@ register_lock_class(struct lockdep_map *lock, unsigned int subclass, int force) */ static struct lock_list *alloc_list_entry(void) { - if (nr_list_entries >= MAX_LOCKDEP_ENTRIES) { + int idx = find_first_zero_bit(list_entries_in_use, + ARRAY_SIZE(list_entries)); + + if (idx >= ARRAY_SIZE(list_entries)) { if (!debug_locks_off_graph_unlock()) return NULL; @@ -899,7 +905,9 @@ static struct lock_list *alloc_list_entry(void) dump_stack(); return NULL; } - return list_entries + nr_list_entries++; + nr_list_entries++; + __set_bit(idx, list_entries_in_use); + return list_entries + idx; } /* @@ -1003,7 +1011,7 @@ static inline void mark_lock_accessed(struct lock_list *lock, unsigned long nr; nr = lock - list_entries; - WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */ + WARN_ON(nr >= ARRAY_SIZE(list_entries)); /* Out-of-bounds, input fail */ lock->parent = parent; lock->class->dep_gen_id = lockdep_dependency_gen_id; } @@ -1013,7 +1021,7 @@ static inline unsigned long lock_accessed(struct lock_list *lock) unsigned long nr; nr = lock - list_entries; - WARN_ON(nr >= nr_list_entries); /* Out-of-bounds, input fail */ + WARN_ON(nr >= ARRAY_SIZE(list_entries)); /* Out-of-bounds, input fail */ return lock->class->dep_gen_id == lockdep_dependency_gen_id; } @@ -4281,13 +4289,14 @@ static void zap_class(struct pending_free *pf, struct lock_class *class) * Remove all dependencies this lock is * involved in: */ - for (i = 0, entry = list_entries; i < nr_list_entries; i++, entry++) { + for_each_set_bit(i, list_entries_in_use, ARRAY_SIZE(list_entries)) { + entry = list_entries + i; if (entry->class != class && entry->links_to != class) continue; + if (__test_and_set_bit(i, pf->list_entries_being_freed)) + continue; + nr_list_entries--; list_del_rcu(&entry->entry); - /* Clear .class and .links_to to avoid double removal. */ - WRITE_ONCE(entry->class, NULL); - WRITE_ONCE(entry->links_to, NULL); } if (list_empty(&class->locks_after) && list_empty(&class->locks_before)) { @@ -4329,8 +4338,9 @@ static bool inside_selftest(void) } /* - * Free all lock classes that are on the pf->zapped_classes list. May be called - * from RCU callback context. + * Free all lock classes that are on the pf->zapped_classes list and also all + * list entries that have been marked as being freed. Called as an RCU + * callback function. May be called from RCU callback context. */ static void free_zapped_classes(struct rcu_head *ch) { @@ -4346,6 +4356,9 @@ static void free_zapped_classes(struct rcu_head *ch) reinit_class(class); } list_splice_init(&pf->zapped_classes, &free_lock_classes); + 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)); graph_unlock(); restore_irqs: raw_local_irq_restore(flags); -- 2.20.0.rc2.403.gdbc3b29805-goog
