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Wed, 04 Dec 2019 17:00:57 -0800 (PST) Received: from localhost ([2401:fa00:8f:203:250d:e71d:5a0a:9afe]) by smtp.gmail.com with ESMTPSA id y22sm9155228pfn.122.2019.12.04.17.00.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 Dec 2019 17:00:56 -0800 (PST) Date: Thu, 5 Dec 2019 10:00:55 +0900 From: Sergey Senozhatsky To: Qian Cai Cc: tytso@mit.edu, Arnd Bergmann , gregkh@linuxfoundation.org, sergey.senozhatsky.work@gmail.com, pmladek@suse.com, rostedt@goodmis.org, Catalin Marinas , will@kernel.org, dan.j.williams@intel.com, peterz@infradead.org, longman@redhat.com, tglx@linutronix.de, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] char/random: silence a lockdep splat with printk() Message-ID: <20191205010055.GO93017@google.com> References: <1573679785-21068-1-git-send-email-cai@lca.pw> <637027D4-BBDD-4AA6-B03C-556060988957@lca.pw> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <637027D4-BBDD-4AA6-B03C-556060988957@lca.pw> User-Agent: Mutt/1.10.1 (2018-07-13) 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: Hi, On (19/12/03 13:46), Qian Cai wrote: > > On Nov 13, 2019, at 4:16 PM, Qian Cai wrote: > > > > From: Sergey Senozhatsky > > > > Sergey didn't like the locking order, > > > > uart_port->lock -> tty_port->lock > > > > uart_write (uart_port->lock) > > __uart_start > > pl011_start_tx > > pl011_tx_chars > > uart_write_wakeup > > tty_port_tty_wakeup > > tty_port_default > > tty_port_tty_get (tty_port->lock) > > > > but those code is so old, and I have no clue how to de-couple it after > > checking other locks in the splat. There is an onging effort to make all > > printk() as deferred, so until that happens, workaround it for now as a > > short-term fix. > > Sergey, could we have a ACK from you so Ted might be able to merge? Not sure if I can ACK it, but overall it makes sense to use deferred printk there. [..] > > > [cai@lca.pw: add a commit log.] > > Signed-off-by: Sergey Senozhatsky > > Signed-off-by: Qian Cai > > --- > > > > Sergey, please let us know if you are fine with the Signed-off-by. A 'Reviewed-by' will suffice. Reviewed-by: Sergey Senozhatsky -ss