diff options
| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2022-05-17 11:16:14 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2022-06-13 10:29:57 +0200 |
| commit | 4051a81774d6d8e28192742c26999d6f29bc0e68 (patch) | |
| tree | d51d31554aa2803d1c0c793006aa50eb96f71e50 /kernel | |
| parent | b13baccc3850ca8b8cccbf8ed9912dbaa0fdf7f3 (diff) | |
| download | lwn-4051a81774d6d8e28192742c26999d6f29bc0e68.tar.gz lwn-4051a81774d6d8e28192742c26999d6f29bc0e68.zip | |
locking/lockdep: Use sched_clock() for random numbers
Since the rewrote of prandom_u32(), in the commit mentioned below, the
function uses sleeping locks which extracing random numbers and filling
the batch.
This breaks lockdep on PREEMPT_RT because lock_pin_lock() disables
interrupts while calling __lock_pin_lock(). This can't be moved earlier
because the main user of the function (rq_pin_lock()) invokes that
function after disabling interrupts in order to acquire the lock.
The cookie does not require random numbers as its goal is to provide a
random value in order to notice unexpected "unlock + lock" sites.
Use sched_clock() to provide random numbers.
Fixes: a0103f4d86f88 ("random32: use real rng for non-deterministic randomness")
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/YoNn3pTkm5+QzE5k@linutronix.de
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/locking/lockdep.c | 2 |
1 files changed, 1 insertions, 1 deletions
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; } |