From: "Jason A. Donenfeld" <Jason@zx2c4.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: linux-kernel@vger.kernel.org,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Waiman Long <longman@redhat.com>,
Boqun Feng <boqun.feng@gmail.com>, Theodore Ts'o <tytso@mit.edu>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH] locking/lockdep: Use sched_clock() for random numbers.
Date: Tue, 17 May 2022 11:53:43 +0200 [thread overview]
Message-ID: <YoNwp+9ko89Tf1ep@zx2c4.com> (raw)
In-Reply-To: <YoNn3pTkm5+QzE5k@linutronix.de>
Hi Sebastian,
Interesting RT consideration. I hope there aren't too many of these
special cases that would necessitate a general mechanism. Fingers
crossed this is the only one.
On Tue, May 17, 2022 at 11:16:14AM +0200, Sebastian Andrzej Siewior wrote:
> - cookie.val = 1 + (prandom_u32() >> 16);
> + cookie.val = 1 + (sched_clock() & 0xffff);
> hlock->pin_count += cookie.val;
I have no idea what the requirements here are. What would happen if you
just did atomic_inc_return(&some_global) instead? That'd be faster
anyhow, and it's not like 16 bits gives you much variance anyway...
Jason
next prev parent reply other threads:[~2022-05-17 9:53 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-17 9:16 [PATCH] locking/lockdep: Use sched_clock() for random numbers Sebastian Andrzej Siewior
2022-05-17 9:53 ` Jason A. Donenfeld [this message]
2022-05-17 9:59 ` Jason A. Donenfeld
2022-05-17 12:08 ` Sebastian Andrzej Siewior
2022-06-13 8:11 ` Peter Zijlstra
2022-06-13 8:05 ` Peter Zijlstra
2022-06-13 8:16 ` Jason A. Donenfeld
2022-06-07 16:51 ` Sebastian Andrzej Siewior
2022-06-12 15:43 ` Sasha Levin
2022-06-13 8:36 ` [tip: locking/urgent] " tip-bot2 for Sebastian Andrzej Siewior
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