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Thu, 05 Sep 2019 19:50:26 -0700 (PDT) Received: from localhost ([175.223.27.235]) by smtp.gmail.com with ESMTPSA id p68sm8147568pfp.9.2019.09.05.19.50.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Sep 2019 19:50:25 -0700 (PDT) Date: Fri, 6 Sep 2019 11:50:22 +0900 From: Sergey Senozhatsky To: Steven Rostedt Cc: Qian Cai , Sergey Senozhatsky , Petr Mladek , Sergey Senozhatsky , Michal Hocko , Eric Dumazet , davem@davemloft.net, netdev@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] net/skbuff: silence warnings under memory pressure Message-ID: <20190906025022.GA1253@jagdpanzerIV> References: <20190904064144.GA5487@jagdpanzerIV> <20190904065455.GE3838@dhcp22.suse.cz> <20190904071911.GB11968@jagdpanzerIV> <20190904074312.GA25744@jagdpanzerIV> <1567599263.5576.72.camel@lca.pw> <20190904144850.GA8296@tigerII.localdomain> <1567629737.5576.87.camel@lca.pw> <20190905113208.GA521@jagdpanzerIV> <1567699393.5576.96.camel@lca.pw> <20190905131413.0aa4e4f1@oasis.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190905131413.0aa4e4f1@oasis.local.home> User-Agent: Mutt/1.12.1 (2019-06-15) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000003, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On (09/05/19 13:14), Steven Rostedt wrote: > > Hmm, from the article, > > > > https://en.wikipedia.org/wiki/Universal_asynchronous_receiver-transmitter > > > > "Since transmission of a single or multiple characters may take a long time > > relative to CPU speeds, a UART maintains a flag showing busy status so that the > > host system knows if there is at least one character in the transmit buffer or > > shift register; "ready for next character(s)" may also be signaled with an > > interrupt." > > I'm pretty sure all serial consoles do a busy loop on the UART and not > use interrupts to notify when it's available. Yes. Besides, we call console drivers with local IRQs disabled. -ss