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From: Ingo Molnar <mingo@kernel.org>
To: lkp@lists.01.org
Subject: Re: [lockdep] b09be676e0 BUG: unable to handle kernel NULL pointer dereference at 000001f2
Date: Wed, 04 Oct 2017 12:31:19 +0200
Message-ID: <20171004103119.sedmwqcfwu3ze5od@gmail.com>
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* Peter Zijlstra <peterz@infradead.org> wrote:

> On Tue, Oct 03, 2017 at 07:18:24PM +0200, Ingo Molnar wrote:
> > Yes, I'll do that tomorrow. I was always a bit unhappy about cross-rele=
ase,
> > because it breaks the 'owner task owns the lock' model.
> =

> Still, you can get real deadlocks with completions...
> =

> > Plus I don't think we found that many real bugs with it
> =

> Every bug found is one less bug. It did find a few.

Certainly, but the total work saved by finding bugs should be balanced agai=
nst the =

additional fragility of lockdep and the ongoing maintenance cost.

Thanks,

	Ingo

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Date: Wed, 4 Oct 2017 12:31:19 +0200
From: Ingo Molnar <mingo@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Fengguang Wu <fengguang.wu@intel.com>,
        Byungchul Park <byungchul.park@lge.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        LKP <lkp@01.org>, Josh Poimboeuf <jpoimboe@redhat.com>
Subject: Re: [lockdep] b09be676e0 BUG: unable to handle kernel NULL pointer
 dereference at 000001f2
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* Peter Zijlstra <peterz@infradead.org> wrote:

> On Tue, Oct 03, 2017 at 07:18:24PM +0200, Ingo Molnar wrote:
> > Yes, I'll do that tomorrow. I was always a bit unhappy about cross-release,
> > because it breaks the 'owner task owns the lock' model.
> 
> Still, you can get real deadlocks with completions...
> 
> > Plus I don't think we found that many real bugs with it
> 
> Every bug found is one less bug. It did find a few.

Certainly, but the total work saved by finding bugs should be balanced against the 
additional fragility of lockdep and the ongoing maintenance cost.

Thanks,

	Ingo