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
| ||
|
Date: Wed, 4 Nov 2015 17:57:24 -0800 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: Peter Zijlstra <peterz@...radead.org> Cc: Dave Jones <davej@...emonkey.org.uk>, Linux Kernel <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...hat.com>, Stephane Eranian <eranian@...il.com>, Andi Kleen <andi@...stfloor.org> Subject: Re: perf related lockdep bug On Wed, Nov 04, 2015 at 03:34:19PM +0100, Peter Zijlstra wrote: > On Wed, Nov 04, 2015 at 06:01:33AM -0800, Paul E. McKenney wrote: > > On Wed, Nov 04, 2015 at 11:28:00AM +0100, Peter Zijlstra wrote: > > > On Wed, Nov 04, 2015 at 11:21:51AM +0100, Peter Zijlstra wrote: > > > > > > > The problem appears to be due to the new RCU expedited grace period > > > > stuff, with rcu_read_unlock() now randomly trying to acquire locks it > > > > previously didn't. > > > > > > > > Lemme go look at those rcu bits again.. > > > > > > Paul, I think this is because of: > > > > > > 8203d6d0ee78 ("rcu: Use single-stage IPI algorithm for RCU expedited grace period") > > > > > > What happens is that the IPI comes in and tags any random > > > rcu_read_unlock() with the special bit, which then goes on and takes > > > locks. > > > > > > Now the problem is that we have scheduler activity inside this lock; > > > the one reported lockdep seems easy enough to fix, see below. > > > > > > I'll got and see if there's more sites than can cause this. > > > > This one only happens during boot time, but it would be good hygiene > > in any case. May I have your SOB on this? > > Of course, > > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org> Thank you, applied as shown below. Thanx, Paul ------------------------------------------------------------------------ commit 05faf451f1239a28fcd63bf4b66c0db57d7b13f9 Author: Peter Zijlstra <peterz@...radead.org> Date: Wed Nov 4 08:22:05 2015 -0800 rcu: Move wakeup out from under rnp->lock This patch removes a potential deadlock hazard by moving the wake_up_process() in rcu_spawn_gp_kthread() out from under rnp->lock. Signed-off-by: Peter Zijlstra <peterz@...radead.org> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index caf3651fa5c9..183445959d00 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -4323,8 +4323,8 @@ static int __init rcu_spawn_gp_kthread(void) sp.sched_priority = kthread_prio; sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); } - wake_up_process(t); raw_spin_unlock_irqrestore(&rnp->lock, flags); + wake_up_process(t); } rcu_spawn_nocb_kthreads(); rcu_spawn_boost_kthreads(); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists