From a0b0fd53e1e67639b303b15939b9c653dbe7a8c4 Mon Sep 17 00:00:00 2001 From: Bart Van Assche Date: Thu, 14 Feb 2019 15:00:46 -0800 Subject: locking/lockdep: Free lock classes that are no longer in use Instead of leaving lock classes that are no longer in use in the lock_classes array, reuse entries from that array that are no longer in use. Maintain a linked list of free lock classes with list head 'free_lock_class'. Only add freed lock classes to the free_lock_classes list after a grace period to avoid that a lock_classes[] element would be reused while an RCU reader is accessing it. Since the lockdep selftests run in a context where sleeping is not allowed and since the selftests require that lock resetting/zapping works with debug_locks off, make the behavior of lockdep_free_key_range() and lockdep_reset_lock() depend on whether or not these are called from the context of the lockdep selftests. Thanks to Peter for having shown how to modify get_pending_free() such that that function does not have to sleep. Signed-off-by: Bart Van Assche Signed-off-by: Peter Zijlstra (Intel) Cc: Andrew Morton Cc: Johannes Berg Cc: Linus Torvalds Cc: Paul E. McKenney Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Waiman Long Cc: Will Deacon Cc: johannes.berg@intel.com Cc: tj@kernel.org Link: https://lkml.kernel.org/r/20190214230058.196511-12-bvanassche@acm.org Signed-off-by: Ingo Molnar --- include/linux/lockdep.h | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) (limited to 'include/linux/lockdep.h') diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index 66eee1ba0f2a..619ec3f26cdc 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -63,7 +63,8 @@ extern struct lock_class_key __lockdep_no_validate__; #define LOCKSTAT_POINTS 4 /* - * The lock-class itself: + * The lock-class itself. The order of the structure members matters. + * reinit_class() zeroes the key member and all subsequent members. */ struct lock_class { /* @@ -72,7 +73,9 @@ struct lock_class { struct hlist_node hash_entry; /* - * global list of all lock-classes: + * Entry in all_lock_classes when in use. Entry in free_lock_classes + * when not in use. Instances that are being freed are on one of the + * zapped_classes lists. */ struct list_head lock_entry; @@ -104,7 +107,7 @@ struct lock_class { unsigned long contention_point[LOCKSTAT_POINTS]; unsigned long contending_point[LOCKSTAT_POINTS]; #endif -}; +} __no_randomize_layout; #ifdef CONFIG_LOCK_STAT struct lock_time { -- cgit v1.2.3