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: Fri, 29 Sep 2017 12:34:24 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Paolo Bonzini <pbonzini@...hat.com> Cc: Boqun Feng <boqun.feng@...il.com>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>, Sasha Levin <levinsasha928@...il.com>, "linux-kernel@...r.kernel.org List" <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...nel.org>, "jiangshanlai@...il.com" <jiangshanlai@...il.com>, "dipankar@...ibm.com" <dipankar@...ibm.com>, Andrew Morton <akpm@...ux-foundation.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, Josh Triplett <josh@...htriplett.org>, Thomas Gleixner <tglx@...utronix.de>, "dhowells@...hat.com" <dhowells@...hat.com>, Eric Dumazet <edumazet@...gle.com>, Fr??d??ric Weisbecker <fweisbec@...il.com>, Oleg Nesterov <oleg@...hat.com>, "bobby.prani@...il.com" <bobby.prani@...il.com>, Radim Kr??m???? <rkrcmar@...hat.com>, kvm@...r.kernel.org Subject: Re: [PATCH v3 tip/core/rcu 40/40] rcu: Make non-preemptive schedule be Tasks RCU quiescent state On Fri, Sep 29, 2017 at 12:01:24PM +0200, Paolo Bonzini wrote: > > Does this mean whenever we get a page fault in a RCU read-side critical > > section, we may hit this? > > > > Could we simply avoid to schedule() in kvm_async_pf_task_wait() if the > > fault process is in a RCU read-side critical section as follow? > > > > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c > > index aa60a08b65b1..291ea13b23d2 100644 > > --- a/arch/x86/kernel/kvm.c > > +++ b/arch/x86/kernel/kvm.c > > @@ -140,7 +140,7 @@ void kvm_async_pf_task_wait(u32 token) > > > > n.token = token; > > n.cpu = smp_processor_id(); > > - n.halted = is_idle_task(current) || preempt_count() > 1; > > + n.halted = is_idle_task(current) || preempt_count() > 1 || rcu_preempt_depth(); > > init_swait_queue_head(&n.wq); > > hlist_add_head(&n.link, &b->list); > > raw_spin_unlock(&b->lock); > > > > (Add KVM folks and list Cced) > > Yes, that would work. Mind to send it as a proper patch? I'm confused, why would we do an ASYNC PF at all here? Thing is, a printk() shouldn't trigger a major fault _ever_. At worst it triggers something like a vmalloc minor fault. And I'm thinking we should not do the whole ASYNC machinery for minor faults.
Powered by blists - more mailing lists