From: Vlastimil Babka <email@example.com>
To: Hyeonggon Yoo <firstname.lastname@example.org>
Cc: kernel test robot <email@example.com>,
Oliver Glitta <firstname.lastname@example.org>,
email@example.com, Mike Rapoport <firstname.lastname@example.org>
Subject: Re: [mm/slub] ae107fa919: BUG:unable_to_handle_page_fault_for_address
Date: Sat, 12 Mar 2022 10:21:25 +0100 [thread overview]
Message-ID: <email@example.com> (raw)
On 3/12/22 02:10, Hyeonggon Yoo wrote:
> On Fri, Mar 11, 2022 at 04:46:00PM +0000, Hyeonggon Yoo wrote:
>> On Fri, Mar 11, 2022 at 04:36:47PM +0100, Vlastimil Babka wrote:
>>> On 3/11/22 15:54, Hyeonggon Yoo wrote:
>>>> On Wed, Mar 09, 2022 at 10:15:31AM +0800, kernel test robot wrote:
>>>>> FYI, we noticed the following commit (built with gcc-9):
>>>>> commit: ae107fa91914f098cd54ab77e68f83dd6259e901 ("mm/slub: use stackdepot to save stack trace in objects")
>>>>> https://git.kernel.org/cgit/linux/kernel/git/vbabka/linux.git slub-stackdepot-v3r0
>>>>> in testcase: boot
>>>>> on test machine: qemu-system-x86_64 -enable-kvm -cpu SandyBridge -smp 2 -m 16G
>>>>> caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):
>>>> [+Cc Vlastimil and linux-mm]
>>> lkp folks: it would be nice if I was CC'd automatically on this, it's a
>>> commit from my git tree and with by s-o-b :)
>>>> I _strongly_ suspect that this is because we don't initialize
>>>> stack_table[i] = NULL when we allocate it from memblock_alloc().
>>> No, Mike (CC'd) suggested to drop the array init cycle, because
>>> memblock_alloc would zero the area anyway.
>> Ah, you are right. My mistake.
>>> There has to be a different
>>> reason. Wondering if dmesg contains the stack depot initialization message
>>> at all...
>> I think I found the reason.
>> This is because of CONFIG_SLUB_DEBUG_ON.
>> It can enable debugging without passing boot parameter.
>> if CONFIG_SLUB_DEBUG_ON=y && slub_debug is not passed, we do not call
>> stack_depot_want_early_init(), but the debugging flags are set.
>> And we only call stack_depot_init() later in kmem_cache_create_usercopy().
>> so it crashed while creating boot cache.
> I tested this, and this was the reason.
> It crashed on CONFIG_SLUB_DEBUG_ON=y because stackdepot always assume
> that it was initialized in boot step, or failed
> But as it didn't even tried to initialize it, stack_table == NULL &&
> stack_depot_disable == false. So accessing *(NULL + <hash value>)
Thanks for finding the cause!
> Ideas? implementing something like kmem_cache_init_early() again?
I think we could simply make CONFIG_SLUB_DEBUG_ON select/depend on
next prev parent reply other threads:[~2022-03-12 9:22 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-09 2:15 [mm/slub] ae107fa919: BUG:unable_to_handle_page_fault_for_address kernel test robot
2022-03-11 14:54 ` Hyeonggon Yoo
2022-03-11 15:36 ` Vlastimil Babka
2022-03-11 16:46 ` Hyeonggon Yoo
2022-03-12 1:10 ` Hyeonggon Yoo
2022-03-12 9:21 ` Vlastimil Babka [this message]
2022-03-12 11:04 ` Hyeonggon Yoo
2022-03-12 12:06 ` Mike Rapoport
2022-03-12 13:08 ` Vlastimil Babka
2022-03-14 16:20 ` Vlastimil Babka
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