Re: [Qemu-devel] broken HMP command: info mtree

[Igor Mammedov <imammedo@redhat.com>]

On Fri, 12 Feb 2016 14:08:32 +0100
Paolo Bonzini <pbonzini@redhat.com> wrote:

> On 12/02/2016 12:17, Daniel P. Berrange wrote:
> > On Fri, Feb 12, 2016 at 12:15:26PM +0100, Igor Mammedov wrote:  
> >> On Thu, 11 Feb 2016 16:35:39 +0100
> >> Igor Mammedov <imammedo@redhat.com> wrote:
> >>  
> >>> executing 'info mtree' from monitor prompt causes infinite loop
> >>> printing it over and over.
> >>>
> >>> to reproduce build current master adn run:
> >>>
> >>> qemu-system-x86_64 -monitor stdio
> >>>
> >>> and then execute 'info mtree' in monitor prompt  
> >>
> >> it bisects to:
> >>
> >> commit 9894dc0cdcc397ee5b26370bc53da6d360a363c2
> >> Author: Daniel P. Berrange <berrange@redhat.com>
> >> Date:   Tue Jan 19 11:14:29 2016 +0000
> >>
> >>     char: convert from GIOChannel to QIOChannel
> >>     
> >>     In preparation for introducing TLS support to the TCP chardev
> >>     backend, convert existing chardev code from using GIOChannel
> >>     to QIOChannel. This simplifies the chardev code by removing
> >>     most of the OS platform conditional code for dealing with
> >>     file descriptor passing.
> >>     
> >>     Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> >>     Message-Id: <1453202071-10289-3-git-send-email-berrange@redhat.com>
> >>     Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> >>
> >>
> >> build with:
> >> ./configure --target-list=x86_64-softmmu --enable-debug 
> >> on RHEL72ish host
> >>
> >> monitor output has to be stdio  
> > 
> > Sigh, so much pain from the chardev code. I'll investigate and send a
> > suitable patch asap.  
> 
> Hmm, I cannot reproduce this though.
Perhaps I'm affected because my stdout goes via remote ssh session.

It looks like monitor tries to flush buffer but succeeds only partially
and returns with EAGAIN and on the next flush attempt it tries to
flush the same buffer again from the first byte again

> 
> Paolo
>