Messages in this thread Patch in this message | | | From | Thomas Gleixner <> | Subject | [GIT pull] locking/urgent for 5.19-rc3 | Date | Sun, 19 Jun 2022 15:12:35 +0200 (CEST) |
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Linus,
please pull the latest locking/urgent branch from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking-urgent-2022-06-19
up to: 4051a81774d6: locking/lockdep: Use sched_clock() for random numbers
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.
Thanks,
tglx
------------------> Sebastian Andrzej Siewior (1): locking/lockdep: Use sched_clock() for random numbers
kernel/locking/lockdep.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c index 81e87280513e..f06b91ca6482 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; }
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