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[59.102.81.67]) by smtp.gmail.com with ESMTPSA id w13-v6sm2178722pgs.89.2018.08.28.08.33.40 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 28 Aug 2018 08:33:42 -0700 (PDT) Date: Wed, 29 Aug 2018 01:33:36 +1000 From: Nicholas Piggin To: Matteo Croce Cc: Greg Kroah-Hartman , Jiri Slaby , Michael Ellerman , Benjamin Herrenschmidt , linux-kernel@vger.kernel.org Subject: Re: VirtIO console hangs Message-ID: <20180829013336.42692195@roar.ozlabs.ibm.com> In-Reply-To: References: <20180829003539.668e514c@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 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! Great thanks for testing it so quickly. I would have thought the return code should cause another poll to trigger. I'll have to read the code again and try to find out what I missed. Thanks, Nick