The following commit has been merged into the locking/core branch of tip: Commit-ID: bd76eca10de2eb9998d5125b08e8997cbf5508d5 Gitweb: https://git.kernel.org/tip/bd76eca10de2eb9998d5125b08e8997cbf5508d5 Author: Boqun Feng <[email protected]> AuthorDate: Fri, 07 Aug 2020 15:42:24 +08:00 Committer: Peter Zijlstra <[email protected]> CommitterDate: Wed, 26 Aug 2020 12:42:04 +02:00
lockdep: Reduce the size of lock_list::distance lock_list::distance is always not greater than MAX_LOCK_DEPTH (which is 48 right now), so a u16 will fit. This patch reduces the size of lock_list::distance to save space, so that we can introduce other fields to help detect recursive read lock deadlocks without increasing the size of lock_list structure. Suggested-by: Peter Zijlstra <[email protected]> Signed-off-by: Boqun Feng <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Link: https://lkml.kernel.org/r/[email protected] --- include/linux/lockdep.h | 2 +- kernel/locking/lockdep.c | 6 +++--- 2 files changed, 4 insertions(+), 4 deletions(-) diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h index 7cae5ea..2275010 100644 --- a/include/linux/lockdep.h +++ b/include/linux/lockdep.h @@ -54,7 +54,7 @@ struct lock_list { struct lock_class *class; struct lock_class *links_to; const struct lock_trace *trace; - int distance; + u16 distance; /* * The parent field is used to implement breadth-first search, and the diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 150686a..668a983 100644 --- a/kernel/locking/lockdep.c +++ b/kernel/locking/lockdep.c @@ -1320,7 +1320,7 @@ static struct lock_list *alloc_list_entry(void) */ static int add_lock_to_list(struct lock_class *this, struct lock_class *links_to, struct list_head *head, - unsigned long ip, int distance, + unsigned long ip, u16 distance, const struct lock_trace *trace) { struct lock_list *entry; @@ -2489,7 +2489,7 @@ check_deadlock(struct task_struct *curr, struct held_lock *next) */ static int check_prev_add(struct task_struct *curr, struct held_lock *prev, - struct held_lock *next, int distance, + struct held_lock *next, u16 distance, struct lock_trace **const trace) { struct lock_list *entry; @@ -2622,7 +2622,7 @@ check_prevs_add(struct task_struct *curr, struct held_lock *next) goto out_bug; for (;;) { - int distance = curr->lockdep_depth - depth + 1; + u16 distance = curr->lockdep_depth - depth + 1; hlock = curr->held_locks + depth - 1; /*
