From: Qian Cai <cai@lca•pw>
To: Michael Ellerman <mpe@ellerman•id.au>,
Bart Van Assche <bvanassche@acm•org>
Cc: Peter Zijlstra <peterz@infradead•org>,
linuxppc-dev@lists•ozlabs.org, Ingo Molnar <mingo@kernel•org>,
linux-kernel@vger•kernel.org
Subject: Re: lockdep warning while booting POWER9 PowerNV
Date: Thu, 05 Sep 2019 10:30:04 -0400 [thread overview]
Message-ID: <1567693804.5576.93.camel@lca.pw> (raw)
In-Reply-To: <87ef0vpfbc.fsf@mpe.ellerman.id.au>
On Thu, 2019-09-05 at 13:55 +1000, Michael Ellerman wrote:
> Bart Van Assche <bvanassche@acm•org> writes:
> > On 8/30/19 2:13 PM, Qian Cai wrote:
> > > https://raw.githubusercontent.com/cailca/linux-mm/master/powerpc.config
> > >
> > > Once in a while, booting an IBM POWER9 PowerNV system (8335-GTH) would
> > > generate
> > > a warning in lockdep_register_key() at,
> > >
> > > if (WARN_ON_ONCE(static_obj(key)))
> > >
> > > because
> > >
> > > key = 0xc0000000019ad118
> > > &_stext = 0xc000000000000000
> > > &_end = 0xc0000000049d0000
> > >
> > > i.e., it will cause static_obj() returns 1.
> >
> > (back from a trip)
> >
> > Hi Qian,
> >
> > Does this mean that on POWER9 it can happen that a dynamically allocated
> > object has an address that falls between &_stext and &_end?
>
> I thought that was true on all arches due to initmem, but seems not.
>
> I guess we have the same problem as s390 and we need to define
> arch_is_kernel_initmem_freed().
Actually, it is in the .bss section. The commit 2d4f567103ff ("KVM: PPC:
Introduce kvm_tmp framework") adds kvm_tmp[] into the .bss section and then free
the rest of unused spaces back to the page allocator.
kernel_init
kvm_guest_init
kvm_free_tmp
free_reserved_area
free_unref_page
free_unref_page_prepare
Later, alloc_workqueue() happens to allocate some pages from there, and triggers
the warning. Not sure what the best way to solve this.
next prev parent reply other threads:[~2019-09-05 14:36 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-30 21:13 lockdep warning while booting POWER9 PowerNV Qian Cai
2019-09-04 16:09 ` Bart Van Assche
2019-09-05 3:55 ` Michael Ellerman
2019-09-05 14:30 ` Qian Cai [this message]
2019-11-21 17:13 ` Qian Cai
2019-11-25 1:12 ` Daniel Axtens
2019-11-25 5:01 ` Michael Ellerman
2019-11-25 12:49 ` Daniel Axtens
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