Merge tag 'locking-urgent-2022-06-19' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

4afb6515 · Linus Torvalds <[email protected]> · 2022-06-19 09:47:41 -05:00

Pull lockdep fix from Thomas Gleixner:
 "A RT fix for lockdep.

  lockdep invokes prandom_u32() to create cookies. This worked until
  prandom_u32() was switched to the real random generator, which takes a
  spinlock for extraction, which does not work on RT when invoked from
  atomic contexts.

  lockdep has no requirement for real random numbers and it turns out
  sched_clock() is good enough to create the cookie. That works
  everywhere and is faster"

* tag 'locking-urgent-2022-06-19' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  locking/lockdep: Use sched_clock() for random numbers

Commit: 4afb65156a79c59fbdbc10abb0bf06ff83f73e23
Parents: 36da9f5f · 4051a817

Merge commit. Changes below are compared with the first parent: 36da9f5f.

Changes

1 files changed · +1 −1

File	Status	Add	Del	Content
kernel/locking/lockdep.c	modified	+1	−1	View file

kernel/locking/lockdep.c

View file

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 81e8728..f06b91c 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -5432,7 +5432,7 @@ static struct pin_cookie __lock_pin_lock(struct lockdep_map *lock)
 			 * be guessable and still allows some pin nesting in
 			 * our u32 pin_count.
 			 */
-			cookie.val = 1 + (prandom_u32() >> 16);
+			cookie.val = 1 + (sched_clock() & 0xffff);
 			hlock->pin_count += cookie.val;
 			return cookie;
 		}