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[109.81.94.157]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3687868ac54sm1264760f8f.28.2024.07.19.03.52.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 19 Jul 2024 03:52:26 -0700 (PDT) Date: Fri, 19 Jul 2024 12:52:25 +0200 From: Michal Hocko To: Vlastimil Babka Cc: Barry Song <21cnbao@gmail.com>, akpm@linux-foundation.org, linux-mm@kvack.org, Barry Song , Uladzislau Rezki , Christoph Hellwig , Lorenzo Stoakes , Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com> Subject: Re: [PATCH RFC] mm: warn potential return NULL for kmalloc_array and kvmalloc_array with __GFP_NOFAIL Message-ID: References: <031ff35b-65f0-4ead-a08f-21711bad5e29@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <031ff35b-65f0-4ead-a08f-21711bad5e29@suse.cz> X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 3757D180026 X-Stat-Signature: wkczfssidjz61f3xt87e3posbztfyayh X-HE-Tag: 1721386347-163161 X-HE-Meta: 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 bvnjN6/P Iqn1HK+ubuD/sRkNpcOb7qlMeiYL7R6Vp6Idpeo8xW7G7fStuYwTDRe5GufurcKEcyfi/b6JbWxrD9WXyk++9jbjwNxbOjKwyS1Q3YrWCQOX2KKZw2li/cKOSNntKx32rTQYhkHwJHkAb/MdxxEsznN7OwzqAX5tE7hS+vvdt1JW07Gx71t0kth9weGoMpBabe7cl6jooAF3BZjPKqL8V6KLj1c5LZjZxbH+aykmgO9n548IOl2nlQycvSXQWB8yPrdGQsk2tgK5yOuF3C2I2wPIps5gukz/WUWxngvrhVXqhsXm2aVDgBbRb3u/pX77IMHl25fwBZ59++5u8GgpvISPjXH3Nl9DLZj6BJUWWyGeEgPAnAHHQc+bLrdwzm30/As4ph9gw3zHRHLnMzOyoPz2zRQ== 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 Fri 19-07-24 12:10:13, Vlastimil Babka wrote: > On 7/19/24 11:33 AM, Michal Hocko wrote: > > On Fri 19-07-24 10:50:07, Vlastimil Babka wrote: > > [...] > >> That wouldn't mean the busy loop is a correct and supported practice. It > >> would just mean it's the least bad of the bad options we have to deal with > >> an allocation that's wrong but we didn't catch soon enough in the development. > > > > So you want to make those potential BUG_ONs hard/soft lockups (not sure > > all arches have a reliable detection) instead? > > I'd expect on a SMP machine there's fair chance of being rescued by kswapd > or other direct reclaimer. I would expect hard/soft lockups... Anyway, the question remains. What is the preferred way to express this is not really supported scenario. -- Michal Hocko SUSE Labs