From: David Hildenbrand <david@redhat.com>
To: Vlastimil Babka <vbabka@suse.cz>,
John Hubbard <jhubbard@nvidia.com>,
Miaohe Lin <linmiaohe@huawei.com>,
akpm@linux-foundation.org
Cc: iamjoonsoo.kim@lge.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] mm/page_isolation: don't putback unisolated page
Date: Thu, 9 Sep 2021 11:37:26 +0200 [thread overview]
Message-ID: <924b4672-0e52-56fb-22a9-b02d8c3ecccf@redhat.com> (raw)
In-Reply-To: <f9cc811d-2932-845d-da0e-eea493981d11@suse.cz>
On 09.09.21 11:07, Vlastimil Babka wrote:
> On 9/9/21 10:56, David Hildenbrand wrote:
>> On 09.09.21 00:42, John Hubbard wrote:
>>> On 9/7/21 2:56 AM, David Hildenbrand wrote:
>>> ...
>>>>> If this can be handled gracefully, then I'd rather go with VM_WARN_ON.
>>>>> Maybe even WARN_ON_ONCE?
>>>>>
>>>>
>>>> I think either VM_BUG_ON() or VM_WARN_ON() -- compiling the runtime
>>>> checks out -- should be good
>>>> enough.
>>>>
>>>> I'd just go with VM_BUG_ON(), because anybody messing with
>>>> __isolate_free_page() should clearly spot
>>>> that we expect the current handling. But no strong opinion.
>>>>
>>>
>>> If in doubt, WARN*() should be preferred over BUG*(). There's a pretty long
>>> history of "don't kill the machine unless you have to" emails about this, let
>>> me dig up one...OK, maybe not the best example, but the tip of the iceberg:
>>
>> Please note the subtle difference between BUG_ON and VM_BUG_ON. We expect
>> VM_BUG_ON to be compiled out on any production system. So it's really only a
>> mean to identify things that really shouldn't be like that during
>> debugging/testing.
>
> IIRC Fedora used to have CONFIG_DEBUG_VM enabled, did it change?
Excellent question. Apparently you are right. Fortunately it's not a
distro to use in production ;)
In kernel-ark:
redhat/configs/fedora/generic/CONFIG_DEBUG_VM:CONFIG_DEBUG_VM=y
While for ARK (rhel-next so to say)
redhat/configs/ark/generic/CONFIG_DEBUG_VM:# CONFIG_DEBUG_VM is not set
So yes, the VM_WARN_ON would then be preferred in that case. But it's
something that should never ever happen unless reviewers and developers
really mess up, so I don't actually would sleep over that. We have other
WARN... that can trigger more easily.
>
>> Using WARN... instead of VM_BUG_ON is even worse for production systems.
>> There are distros that set panic_on_warn, essentially converting WARN...
>> into BUG...
>
> Uh, does any distro really do that?
Apparently, so I was told by Greg a year ago or so when wanting to add
WARN_ON(). The advisory is to us pr_warn_once() instead. I rememebr it
was a debian based distro.
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2021-09-09 9:37 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-04 9:18 [PATCH] mm/page_isolation: don't putback unisolated page Miaohe Lin
2021-09-06 9:40 ` David Hildenbrand
2021-09-06 11:32 ` Miaohe Lin
2021-09-06 11:50 ` David Hildenbrand
2021-09-06 12:01 ` David Hildenbrand
2021-09-06 12:08 ` Miaohe Lin
2021-09-06 12:02 ` David Hildenbrand
2021-09-06 12:11 ` David Hildenbrand
2021-09-06 12:45 ` Miaohe Lin
2021-09-06 12:49 ` David Hildenbrand
2021-09-07 1:46 ` Miaohe Lin
2021-09-07 9:52 ` David Hildenbrand
2021-09-07 8:08 ` Vlastimil Babka
2021-09-07 9:56 ` David Hildenbrand
2021-09-08 22:42 ` John Hubbard
2021-09-09 8:56 ` David Hildenbrand
2021-09-09 9:07 ` Vlastimil Babka
2021-09-09 9:37 ` David Hildenbrand [this message]
2021-09-09 16:50 ` John Hubbard
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