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[71.184.117.43]) by smtp.gmail.com with ESMTPSA id 29sm5601981qkp.86.2019.10.05.18.10.12 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 05 Oct 2019 18:10:12 -0700 (PDT) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable From: Qian Cai Mime-Version: 1.0 (1.0) Subject: Re: [PATCH] mm/page_isolation: fix a deadlock with printk() Date: Sat, 5 Oct 2019 21:10:11 -0400 Message-Id: References: <20191005174423.23f2db80872a9365009f398a@linux-foundation.org> Cc: mhocko@kernel.org, sergey.senozhatsky.work@gmail.com, pmladek@suse.com, rostedt@goodmis.org, peterz@infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org In-Reply-To: <20191005174423.23f2db80872a9365009f398a@linux-foundation.org> To: Andrew Morton 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 5, 2019, at 8:44 PM, Andrew Morton wrot= e: >=20 > There is no "console_lock". Please be much more specific. >=20 >> It is easier to avoid, >>=20 >> zone_lock -> console_lock >>=20 >> rather than fixing the opposite. >=20 > "ease" isn't the main objective. A more important question is "what > makes sense". We should be able to call printk() from anywhere, any > time under any conditions. That can't be done 100% but it is the > objective. printk() should be robust and not being able to call > printk() while holding zone->lock isn't robust! >=20 > btw, this: >=20 > : It is unsafe to call printk() while zone->lock was held, i.e., > : > : zone->lock --> console_sem >=20 > doesn't make a lot of sense. console_sem is a sleeping lock so > attempting to acquire it (with down()!) under spinlock is a huge bug.=20 > Again, please be careful with the descriptions. Sorry, It is console_owner_lock.=