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Wed, 20 Nov 2019 17:05:31 -0800 (PST) Received: from localhost ([2401:fa00:8f:203:250d:e71d:5a0a:9afe]) by smtp.gmail.com with ESMTPSA id m6sm427110pgl.42.2019.11.20.17.05.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 20 Nov 2019 17:05:30 -0800 (PST) Date: Thu, 21 Nov 2019 10:05:27 +0900 From: Sergey Senozhatsky To: Petr Mladek Cc: Sergey Senozhatsky , Sergey Senozhatsky , Qian Cai , Steven Rostedt , 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: <20191121010527.GB191121@google.com> References: <1567599263.5576.72.camel@lca.pw> <20190904144850.GA8296@tigerII.localdomain> <1567629737.5576.87.camel@lca.pw> <20190905113208.GA521@jagdpanzerIV> <1573751570.5937.122.camel@lca.pw> <20191118152738.az364dczadskgimc@pathway.suse.cz> <20191119004119.GC208047@google.com> <20191119094134.6hzbjc7l5ite6bpg@pathway.suse.cz> <20191120013005.GA3191@tigerII.localdomain> <20191120161334.p63723g4jyk6k7p3@pathway.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191120161334.p63723g4jyk6k7p3@pathway.suse.cz> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000745, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On (19/11/20 17:13), Petr Mladek wrote: [..] > It is the first time that I hear about problem caused by the > irq_work(). But we deal with deadlocks caused by wake_up() for years. > It would be like replacing a lightly dripping tap with a heavily > dripping one. > > I see reports with WARN() from scheduler code from time to time. > I would get reports about silent death instead. Just curious, how many of those WARN() come under rq lock or pi_lock? // this is real question > RT guys are going to make printk() fully lockless. It would be > really great achievement. irq_work is lockless. While wake_up() > is not. > > There must be a better way how to break the infinite loop caused > by the irq_work. A lockless wake_up() would do :) -ss