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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id m91sm2238816qte.8.2019.10.10.02.01.45 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 10 Oct 2019 02:01:45 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Qian Cai Mime-Version: 1.0 (1.0) Subject: Re: [PATCH v2] mm/page_isolation: fix a deadlock with printk() Date: Thu, 10 Oct 2019 05:01:44 -0400 Message-Id: <6AAB77B5-092B-43E3-9F4B-0385DE1890D9@lca.pw> References: <20191009162339.GI6681@dhcp22.suse.cz> Cc: Petr Mladek , Christian Borntraeger , Heiko Carstens , sergey.senozhatsky.work@gmail.com, rostedt@goodmis.org, peterz@infradead.org, linux-mm@kvack.org, john.ogness@linutronix.de, akpm@linux-foundation.org, Vasily Gorbik , Peter Oberparleiter , david@redhat.com, linux-kernel@vger.kernel.org In-Reply-To: <20191009162339.GI6681@dhcp22.suse.cz> To: Michal Hocko X-Mailer: iPhone Mail (17A860) 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: > On Oct 9, 2019, at 12:23 PM, Michal Hocko wrote: >=20 > If this was only about the memory offline code then I would agree. But > we are talking about any printk from the zone->lock context and that is > a bigger deal. Besides that it is quite natural that the printk code > should be more universal and allow to be also called from the MM > contexts as much as possible. If there is any really strong reason this > is not possible then it should be documented at least. Where is the best place to document this? I am thinking about under the =E2=80= =9Cstruct zone=E2=80=9D definition=E2=80=99s lock field in mmzone.h. Does workaround this potential deadlock and fix a few lockdep false positive= s for free count as a really strong reason?=