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Wed, 09 Oct 2019 22:14:19 -0700 (PDT) Received: from localhost ([39.7.28.208]) by smtp.gmail.com with ESMTPSA id bx18sm3109042pjb.26.2019.10.09.22.14.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 09 Oct 2019 22:14:18 -0700 (PDT) Date: Thu, 10 Oct 2019 14:12:01 +0900 From: Sergey Senozhatsky To: Michal Hocko Cc: Peter Oberparleiter , Qian Cai , Christian Borntraeger , Petr Mladek , akpm@linux-foundation.org, sergey.senozhatsky.work@gmail.com, rostedt@goodmis.org, peterz@infradead.org, linux-mm@kvack.org, john.ogness@linutronix.de, david@redhat.com, linux-kernel@vger.kernel.org, Heiko Carstens , Vasily Gorbik Subject: Re: [PATCH v2] mm/page_isolation: fix a deadlock with printk() Message-ID: <20191010051201.GA78180@jagdpanzerIV> References: <1570228005-24979-1-git-send-email-cai@lca.pw> <20191007143002.l37bt2lzqtnqjqxu@pathway.suse.cz> <20191007144937.GO2381@dhcp22.suse.cz> <20191008074357.f33f6pbs4cw5majk@pathway.suse.cz> <20191008082752.GB6681@dhcp22.suse.cz> <1570550917.5576.303.camel@lca.pw> <1157b3ae-006e-5b8e-71f0-883918992ecc@linux.ibm.com> <20191009142623.GE6681@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191009142623.GE6681@dhcp22.suse.cz> User-Agent: Mutt/1.12.2 (2019-09-21) 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 (10/09/19 16:26), Michal Hocko wrote: > On Wed 09-10-19 15:56:32, Peter Oberparleiter wrote: > [...] > > A generic solution would be preferable from my point of view though, > > because otherwise each console driver owner would need to ensure that any > > lock taken in their console.write implementation is never held while > > memory is allocated/released. > > Considering that console.write is called from essentially arbitrary code > path IIUC then all the locks used in this path should be pretty much > tail locks or console internal ones without external dependencies. That's a good expectation, but I guess it's not always the case. One example might be NET console - net subsystem locks, net device drivers locks, maybe even some MM locks (skb allocations?). But even more "commonly used" consoles sometimes break that expectation. E.g. 8250 serial8250_console_write() serial8250_modem_status() wake_up_interruptible() And so on. -ss