Messages in this thread | | | From | "Wang, Yalin" <> | Date | Thu, 17 Oct 2013 09:51:34 +0800 | Subject | RE: BUG report about ipt_do_table( ) |
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Hi Will,
I am happy to notify that our stability test has passed, And this Crash don't happen again, So seems this patch work now .
We has merged it into our release SW . Could I know if this patch will be delivered into kernel Mainline by you ?
Thanks again !
-----Original Message----- From: Wang, Yalin Sent: Friday, October 11, 2013 7:15 PM To: 'Will Deacon' Cc: 'linux-arm-msm-owner@vger.kernel.org'; linux-kernel@vger.kernel.org; Peng, Arthur; Zhang, Bojie; Gu, Youcai 1 (EXT); Alevoor, Raghavendra 2 Subject: RE: BUG report about ipt_do_table( )
Hi Will,
Thanks for your clarification .
I have merged the patch, And need wait some time to get The test result , You know that this BUG is not easy to reproduce, It's very infrequent. Maybe we need run several times stability test to Make sure the patch works .
I will update to you the result as soon as possible !
Thanks
-----Original Message----- From: Will Deacon [mailto:will.deacon@arm.com] Sent: Friday, October 11, 2013 7:03 PM To: Wang, Yalin Cc: 'linux-arm-msm-owner@vger.kernel.org'; linux-kernel@vger.kernel.org; Peng, Arthur; Zhang, Bojie; Gu, Youcai 1 (EXT); Alevoor, Raghavendra 2 Subject: Re: BUG report about ipt_do_table( )
On Fri, Oct 11, 2013 at 02:50:24AM +0100, Wang, Yalin wrote: > Hi Will,
Hello again,
> Maybe I know your meaning , > If it use spinlock to protected the shared data, The bug will not > happen, because spinlock will Use DSB( ) to sync .
Actually, the dsb is for something else (the sev). It is the smp_mb() call which guarantees the ordering of critical sections with respect to spinlock operations.
> Unluckily, here, it use a special seqcount_t( ) (see get_counters( ) > function)
Well, there is a comment about a write_lock being held, so you should be ok if that's true. The issue I saw was with the newinfo population, as I described in my earlier mail.
> To make sure there is no others using the old data, Before release the > old data, this is much like RCU Work, but RCU use rcu_assign_pointer( > ) --> Which use smp_wmb( ) , so it's safe, am I right ?
RCU is safe. There are *many* weakly ordered architectures on which Linux runs, so I don't think you have to worry too much about the core data structures and locking/synchronisation/atomic primitives. The major scope for errors is in lockless code, where the barrier usage is explicit.
> In my patch, I use mb( ), because this macro Is DSB( ) , while > smp_wmb( ) is DMS( ), I just think DSB is much strict than DMS, mmm.. > so , DSM( ) or DMS ( ) are both ok ?
I think you're getting confused with your barriers. We have two memory barriers on ARM: dmb and dsb. dmb is sufficient to enforce ordering of observability. dsb is used to enforce completion.
> The whitepaper I use is here: > https://www.google.com/#q=cortex+a15+microarchitecture > > the first: [PDF] Exploring the Design of the Cortex-A15 Processor - > ARM > > I just search in Google, and you know that qcom don't release Much > document about its krait cpu's micro architecture details, I just use > cortex-a15 for a reference, I am not sure if their pipeline ( > load/store unit) are the same,
I think the lawyers would have a field day if the pipelines were the same! You really can't use an A15 slide-deck to infer micro-architectural details about Krait.
Please can you test the patch I sent you yesterday?
Will
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