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[59.102.81.67]) by smtp.gmail.com with ESMTPSA id e14-v6sm15154288pff.128.2018.08.31.15.57.29 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 31 Aug 2018 15:57:31 -0700 (PDT) Date: Sat, 1 Sep 2018 08:57:25 +1000 From: Nicholas Piggin To: Matteo Croce Cc: Greg Kroah-Hartman , Jiri Slaby , Michael Ellerman , Benjamin Herrenschmidt , linux-kernel@vger.kernel.org, Lorenzo Bianconi Subject: Re: VirtIO console hangs Message-ID: <20180901085725.4dcd9cac@roar.ozlabs.ibm.com> In-Reply-To: References: <20180829003539.668e514c@roar.ozlabs.ibm.com> <20180831134943.7f516fed@roar.ozlabs.ibm.com> X-Mailer: Claws Mail 3.17.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 31 Aug 2018 15:17:44 +0000 Matteo Croce wrote: > On Fri, Aug 31, 2018 at 3:49 AM Nicholas Piggin wrote: > > > > On Tue, 28 Aug 2018 15:00:14 +0000 > > Matteo Croce wrote: > > > > > On Tue, Aug 28, 2018 at 2:35 PM Nicholas Piggin wrote: > > > > > > > > On Tue, 28 Aug 2018 12:54:08 +0000 > > > > Matteo Croce wrote: > > > > > > > > > With kernel 4.19.0-rc1 virtio_console hangs very often. > > > > > I can always trigger the bug by pasting some characters in the > > > > > terminal window, the console will stop receiving keypresses, but I can > > > > > still see output from the console. > > > > > Stangely, logging in the VM via SSH and sending lot of data to hvc0, > > > > > like 'dmesg >/dev/hvc0' will fix the issue until the next paste. > > > > > > > > > > I did a git bisect and I've found that this is the offending commit, > > > > > reverting it fixes it. > > > > > > > > > > Cheers, > > > > > > > > > > commit ec97eaad1383ab2500fcf9a07ade6044fbcc67f5 > > > > > Author: Nicholas Piggin > > > > > Date: Tue May 1 00:55:54 2018 +1000 > > > > > > > > > > tty: hvc: hvc_poll() break hv read loop > > > > > > > > Thanks for the report. I can't immediately see what the problem > > > > is. Can you try get a stack trace of where it is stuck? > > > > > > > > > > I tried but didn't get one. > > > > > > > Perhaps try this patch if you have time (it's a bit of a shot > > > > in the dark). > > > > > > > > > > Yes it seems to fix. Thanks! > > > > Okay sorry for the delay, I can reproduce it here and found a better > > fix, if I could trouble you to test again. > > > > [PATCH] tty: hvc: hvc_poll() fix read loop hang > > > > Hi Nicholas, > > the patch works, but now pasting text inside the terminal is extremely > slow, it feels worse than a 9600 baud serial line. > > Btw, I had to apply the patch by hand as it was corrupted, some lines > were collapsed into one. Oh, when you revert the above commit, does it fix the speed problem as well? I realise I'm testing with a remote machine that probably is not connected with much better than 9600 baud... I will set up a local test. Thanks, Nick