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: Thu, 08 Aug 2013 09:17:12 +0800 From: Lai Jiangshan <laijs@...fujitsu.com> To: Carsten Emde <C.Emde@...dl.org> CC: paulmck@...ux.vnet.ibm.com, Steven Rostedt <rostedt@...dmis.org>, Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org Subject: Re: [PATCH 0/8] rcu: Ensure rcu read site is deadlock-immunity On 08/08/2013 03:29 AM, Carsten Emde wrote: > Hi Paul, > >>> Although all articles declare that rcu read site is deadlock-immunity. >>> It is not true for rcu-preempt, it will be deadlock if rcu read site >>> overlaps with scheduler lock. >> >> The real rule is that if the scheduler does its outermost rcu_read_unlock() >> with one of those locks held, it has to have avoided enabling preemption >> through the entire RCU read-side critical section. >> >> That said, avoiding the need for this rule would be a good thing. >> >> How did you test this? The rcutorture tests will not exercise this. >> (Intentionally so, given that it can deadlock!) >> >>> ec433f0c, 10f39bb1 and 016a8d5b just partially solve it. But rcu read site >>> is still not deadlock-immunity. And the problem described in 016a8d5b >>> is still existed(rcu_read_unlock_special() calls wake_up). >>> >>> The problem is fixed in patch5. >> >> This is going to require some serious review and testing. One requirement >> is that RCU priority boosting not persist significantly beyond the >> re-enabling of interrupts associated with the irq-disabled lock. To do >> otherwise breaks RCU priority boosting. At first glance, the added >> set_need_resched() might handle this, but that is part of the review >> and testing required. >> >> Steven, would you and Carsten be willing to try this and see if it >> helps with the issues you are seeing in -rt? (My guess is "no", since >> a deadlock would block forever rather than waking up after a couple >> thousand seconds, but worth a try.) > Your guess was correct, applying this patch doesn't heal the NO_HZ_FULL+PREEMPT_RT_FULL 3.10.4 based system; it still is hanging at -> synchronize_rcu -> wait_rcu_gp. > > -Carsten. > I didn't find the problem you reported, could you give me a url? Thanx, Lai -- 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