Re: [Qemu-devel] [PATCH v6 1/4] tests: Add test-listen - a stress test for QEMU socket listen

[Knut Omang <knut.omang@oracle.com>]

On Mon, 2017-08-07 at 09:45 +0100, Daniel P. Berrange wrote:
> On Sat, Jul 29, 2017 at 11:18:15PM +0200, Knut Omang wrote:
> > There's a potential race condition between multiple bind()'s
> > attempting to bind to the same port, which occasionally
> > allows more than one bind to succeed against the same port.
> > 
> > When a subsequent listen() call is made with the same socket
> > only one will succeed.
> > 
> > The current QEMU code does however not take this situation into account
> > and the listen will cause the code to break out and fail even
> > when there are actually available ports to use.
> > 
> > This test exposes two subtests:
> > 
> > /socket/listen-serial
> > /socket/listen-compete
> > 
> > The "compete" subtest creates a number of threads and have them all trying to bind
> > to the same port with a large enough offset input to
> > allow all threads to get it's own port.
> > The "serial" subtest just does the same, except in series in a
> > single thread.
> > 
> > The serial version passes, probably in most versions of QEMU.
> > 
> > The parallel version exposes the problem in a relatively reliable way,
> > eg. it fails a majority of times, but not with a 100% rate, occasional
> > passes can be seen. Nevertheless this is quite good given that
> > the bug was tricky to reproduce and has been left undetected for
> > a while.
> > 
> > The problem seems to be present in all versions of QEMU.
> > 
> > The original failure scenario occurred with VNC port allocation
> > in a traditional Xen based build, in different code
> > but with similar functionality.
> > 
> > Reported-by: Bhavesh Davda <bhavesh.davda@oracle.com>
> > Signed-off-by: Knut Omang <knut.omang@oracle.com>
> > Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
> > Reviewed-by: Bhavesh Davda <bhavesh.davda@oracle.com>
> > Reviewed-by: Girish Moodalbail <girish.moodalbail@oracle.com>
> > ---
> >  tests/Makefile.include |   2 +-
> >  tests/test-listen.c    | 253 ++++++++++++++++++++++++++++++++++++++++++-
> >  2 files changed, 255 insertions(+)
> >  create mode 100644 tests/test-listen.c
> > 
> > diff --git a/tests/Makefile.include b/tests/Makefile.include
> > index 7af278d..b37c0c8 100644
> > --- a/tests/Makefile.include
> > +++ b/tests/Makefile.include
> > @@ -128,6 +128,7 @@ check-unit-y += tests/test-bufferiszero$(EXESUF)
> >  gcov-files-check-bufferiszero-y = util/bufferiszero.c
> >  check-unit-y += tests/test-uuid$(EXESUF)
> >  check-unit-y += tests/ptimer-test$(EXESUF)
> > +#check-unit-y += tests/test-listen$(EXESUF)
> >  gcov-files-ptimer-test-y = hw/core/ptimer.c
> >  check-unit-y += tests/test-qapi-util$(EXESUF)
> >  gcov-files-test-qapi-util-y = qapi/qapi-util.c
> > @@ -769,6 +770,7 @@ tests/test-arm-mptimer$(EXESUF): tests/test-arm-mptimer.o
> >  tests/test-qapi-util$(EXESUF): tests/test-qapi-util.o $(test-util-obj-y)
> >  tests/numa-test$(EXESUF): tests/numa-test.o
> >  tests/vmgenid-test$(EXESUF): tests/vmgenid-test.o tests/boot-sector.o tests/acpi-utils.o
> > +tests/test-listen$(EXESUF): tests/test-listen.o $(test-util-obj-y)
> >  
> >  tests/migration/stress$(EXESUF): tests/migration/stress.o
> >  	$(call quiet-command, $(LINKPROG) -static -O3 $(PTHREAD_LIB) -o $@ $< ,"LINK","$(TARGET_DIR)$@")
> > diff --git a/tests/test-listen.c b/tests/test-listen.c
> > new file mode 100644
> > index 0000000..5c07537
> > --- /dev/null
> > +++ b/tests/test-listen.c
> > @@ -0,0 +1,253 @@
> > +/*
> > + * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
> > + *    Author: Knut Omang <knut.omang@oracle.com>
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2
> > + * as published by the Free Software Foundation.
> 
> Can you change that to "version 2 or later" - per the LICENSE file, we don't
> accept contributions under "version 2 only" except for 4 specific subdirs:
> 
> 
>   "As of July 2013, contributions under version 2 of the GNU General Public
>    License (and no later version) are only accepted for the following files
>    or directories: bsd-user/, linux-user/, hw/vfio/, hw/xen/xen_pt*."

Oh, sorry - I wasn't aware of this, +"...or later" is fine with me.
Would you like me to send a v7 of the set with only that change, or can you amend 
it as part of the merge?

Thanks,
Knut

> 
> > + *
> > + * Test parallel port listen configuration with
> > + * dynamic port allocation
> > + */
> 
> 
> Regards,
> Daniel