linux-kernel - Re: [tip: locking/core] lockdep: Fix lockdep recursion

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Thu, 15 Oct 2020 11:52:35 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Paul E. McKenney" <paulmck@...nel.org>
Cc:     Boqun Feng <boqun.feng@...il.com>, Qian Cai <cai@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...nel.org>, x86 <x86@...nel.org>,
        linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>
Subject: Re: [tip: locking/core] lockdep: Fix lockdep recursion

On Thu, Oct 15, 2020 at 11:49:26AM +0200, Peter Zijlstra wrote:
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -1764,8 +1764,7 @@ static bool rcu_gp_init(void)
>  		smp_mb(); // Pair with barriers used when updating ->ofl_seq to odd values.
>  		firstseq = READ_ONCE(rnp->ofl_seq);
>  		if (firstseq & 0x1)
> -			while (firstseq == smp_load_acquire(&rnp->ofl_seq))
> -				schedule_timeout_idle(1);  // Can't wake unless RCU is watching.
> +			smp_cond_load_relaxed(&rnp->ofl_seq, VAL == firstseq);

My bad, that should be: VAL != firstseq.

>  		smp_mb(); // Pair with barriers used when updating ->ofl_seq to even values.
>  		raw_spin_lock(&rcu_state.ofl_lock);
>  		raw_spin_lock_irq_rcu_node(rnp);