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[109.81.26.204]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-454d5032e17sm71179105e9.5.2025.07.10.11.29.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 10 Jul 2025 11:29:15 -0700 (PDT) Date: Thu, 10 Jul 2025 20:29:14 +0200 From: Michal Hocko To: Lorenzo Stoakes Cc: Alexey Dobriyan , akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, David Hildenbrand , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan Subject: Re: [PATCH] mm: implement "memory.oops_if_bad_pte=1" boot option Message-ID: References: <4e1b7d2d-ed54-4e0a-a0a4-906b14d9cd41@p183> <525a4060-2c8b-40c5-b4bd-b9c47de94f0f@lucifer.local> <72956765-39e0-445a-b381-6bbc54046544@p183> <5242fca8-4a17-4ff8-a624-08778fc64f19@lucifer.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5242fca8-4a17-4ff8-a624-08778fc64f19@lucifer.local> X-Rspam-User: X-Stat-Signature: a3amxqh4axpxqt7t69dcqs7es5huxnn5 X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 0AE031C0009 X-HE-Tag: 1752172156-778691 X-HE-Meta: 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 ph2M36p5 HVn5viyLXgj1IhSDOFy7VJLGcM8UO7MfHDyS5FTqrEYGpfbMcp/GeFEQDg+JgnrSSvrWFt+aXVLY/aE3UwpwgQEy902WSpvQlXeE0QPI+nDA2PiMoXQuGB8WjmkUmc7RrMZI8sJMesKPcU6M6JTjVm15AV3TAbeFkP+qNEUxjrjJ/spIac8cYcyMwNf5lI7UrCaT1CRANap0C/nXOW1Ti+6BqzX92R8PLAbybQztIzKyYVHz1sqWMa8ZV8IZxO6ADVzyJJwG3hc/a7nae/vs7gGGaSWZZpxy0q7VkACdHOkg1G8nRCz19X+e3hJ8JVfjZMKyFq44M2jKwpqvM7FVOym0maSp+lMWAnQktx5OodMhAU1Y= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu 10-07-25 18:02:07, Lorenzo Stoakes wrote: > OK I wasn't clear enough I guess - NAK. Completely Agreed! Because.... > This is not upstreamable, nor anything like it. > > On Thu, Jul 10, 2025 at 07:57:00PM +0300, Alexey Dobriyan wrote: > > On Thu, Jul 10, 2025 at 05:16:52PM +0100, Lorenzo Stoakes wrote: [...] > > > You seem to be using BUG_ON() to _maybe_ cause a panic, maybe not, but by > > > doing this you're inferring that there's unrecoverable system instability, > > > which isf clearly not the case. .... of exactly this. I believe we have already/finally established that BUG_ON (not even VM_BUG_ON) is a sensible debugging tool. In this particular case it is not even clear when the page table got corrupted and it could have happened loong before we notice that so crash dumping right away doesn't really guarantee anything. So if this really helped in some specific situations and there is hope it might help in the future then I believe [...] > > > Overall I suspect there's one single case you're worried about, that really > > > you want to put a WARN_ON_ONCE() against - then you can panic_on_warn and > > > get what you want. is exactly what you should do. But even then dump_stack should be dropped to not duplicate the information printed etc. -- Michal Hocko SUSE Labs