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Date: Wed, 16 Oct 2019 10:20:22 +0200
From: Michal Hocko <mhocko@kernel.org>
To: Anshuman Khandual <anshuman.khandual@arm.com>
Subject: Re: [PATCH V6 0/2] mm/debug: Add tests validating architecture page
 table helpers
Message-ID: <20191016082022.GN317@dhcp22.suse.cz>
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Cc: Mark Rutland <mark.rutland@arm.com>, linux-ia64@vger.kernel.org,
 linux-sh@vger.kernel.org, Peter Zijlstra <peterz@infradead.org>,
 James Hogan <jhogan@kernel.org>,
 Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>,
 Heiko Carstens <heiko.carstens@de.ibm.com>, linux-kernel@vger.kernel.org,
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 Kees Cook <keescook@chromium.org>,
 Masahiro Yamada <yamada.masahiro@socionext.com>,
 Mark Brown <broonie@kernel.org>, Qian Cai <cai@lca.pw>,
 "Kirill A . Shutemov" <kirill@shutemov.name>,
 Dan Williams <dan.j.williams@intel.com>, Vlastimil Babka <vbabka@suse.cz>,
 Sri Krishna chowdary <schowdary@nvidia.com>,
 Ard Biesheuvel <ard.biesheuvel@linaro.org>,
 Greg Kroah-Hartman <gregkh@linuxfoundation.org>, linux-mips@vger.kernel.org,
 Ralf Baechle <ralf@linux-mips.org>, Paul Burton <paul.burton@mips.com>,
 Mike Rapoport <rppt@linux.vnet.ibm.com>, Vineet Gupta <vgupta@synopsys.com>,
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 Andrew Morton <akpm@linux-foundation.org>, linuxppc-dev@lists.ozlabs.org,
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On Tue 15-10-19 20:51:11, Anshuman Khandual wrote:
> 
> 
> On 10/15/2019 08:11 PM, Qian Cai wrote:
> > The x86 will crash with linux-next during boot due to this series (v5) with the
> > config below plus CONFIG_DEBUG_VM_PGTABLE=y. I am not sure if v6 would address
> > it.
> > 
> > https://raw.githubusercontent.com/cailca/linux-mm/master/x86.config
> > 
> > [   33.862600][    T1] page:ffffea0009000000 is uninitialized and poisoned
> > [   33.862608][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff
> > ffffff871140][    T1]  ? _raw_spin_unlock_irq+0x27/0x40
> > [   33.871140][    T1]  ? rest_init+0x307/0x307
> > [   33.871140][    T1]  kernel_init+0x11/0x139
> > [   33.871140][    T1]  ? rest_init+0x307/0x307
> > [   33.871140][    T1]  ret_from_fork+0x27/0x50
> > [   33.871140][    T1] Modules linked in:
> > [   33.871140][    T1] ---[ end trace e99d392b0f7befbd ]---
> > [   33.871140][    T1] RIP: 0010:alloc_gigantic_page_order+0x3fe/0x490
> 
> Hmm, with defconfig (DEBUG_VM=y and DEBUG_VM_PGTABLE=y) it does not crash but
> with the config above, it does. Just wondering if it is possible that these
> pages might not been initialized yet because DEFERRED_STRUCT_PAGE_INIT=y ?

Quite likely. You need to wait for page_alloc_init_late to finish.
> 
> [   13.898549][    T1] page:ffffea0005000000 is uninitialized and poisoned
> [   13.898549][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
> [   13.898549][    T1] raw: ffffffffffffffff ffffffffffffffff ffffffffffffffff ffffffffffffffff
> [   13.898549][    T1] page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p))
> [   13.898549][    T1] ------------[ cut here ]------------
> [   13.898549][    T1] kernel BUG at ./include/linux/mm.h:1107!
> [   13.898549][    T1] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI
> [   13.898549][    T1] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.4.0-rc3-next-20191015+ #

-- 
Michal Hocko
SUSE Labs