lkml.org 
[lkml]   [2022]   [Jun]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[GIT pull] locking/urgent for 5.19-rc3
Date
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;
}
\
 
 \ /
  Last update: 2022-06-19 15:15    [W:0.153 / U:0.364 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site