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

[Knut Omang]

On Mon, 2017-08-07 at 11:27 +0100, Daniel P. Berrange wrote:
> On Mon, Aug 07, 2017 at 11:21:25AM +0200, Knut Omang wrote:
> > 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 <address@hidden>
> > > > Signed-off-by: Knut Omang <address@hidden>
> > > > Reviewed-by: Yuval Shaia <address@hidden>
> > > > Reviewed-by: Bhavesh Davda <address@hidden>
> > > > Reviewed-by: Girish Moodalbail <address@hidden>
> > > > ---
> > > >  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 <address@hidden>
> > > > + *
> > > > + * 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?
> 
> Since its a copyright statement, I'd prefer if you just sent a v7. I've no
> other comments, so will queue it for merge once you resend, and send a pull
> request once 2.11 opens up.

Ok, will do,

Thanks,
Knut

> Regards,
> Daniel