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Libvirt provides a portable, long term stable C API for managing the virtualization technologies provided by many operating systems. It includes support for QEMU, KVM, Xen, LXC, bhyve, Virtuozzo, VMware vCenter and ESX, VMware Desktop, Hyper-V, VirtualBox and the POWER Hypervisor.
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Eric Blake cefe0ba3db blockjob: split out block info driver handling 
The qemu implementation for virDomainGetBlockJobInfo() has a
minor bug: it grabs the qemu job with intent to QEMU_JOB_MODIFY,
which means it cannot be run in parallel with any other
domain-modifying command.  Among others, virDomainBlockJobAbort()
is such a modifying command, and it defaults to being
synchronous, and can wait as long as several seconds to ensure
that the job has actually finished.  Due to the job rules, this
means a user cannot obtain status about the job during that
timeframe, even though we know that some client management code
exists which is using a polling loop on status to see when a job
finishes.

This bug has been present ever since blockpull support was first
introduced (commit b976165, v0.9.4 in Jul 2011), all because we
stupidly tried to cram too much multiplexing through a single
helper routine, but was made worse in 97c59b9 (v1.2.7) when
BlockJobAbort was fixed to wait longer.  It's time to disentangle
some of the mess in qemuDomainBlockJobImpl, and in the process
relax block job query to use QEMU_JOB_QUERY, since it can safely
be used in parallel with any long running modify command.

Technically, there is one case where getting block job info can
modify domain XML - we do snooping to see if a 2-phase job has
transitioned into the second phase, for an optimization in the
case of old qemu that lacked an event for the transition.  I
claim this optimization is safe (the jobs are all about modifying
qemu state, not necessarily xml state); but if it proves to be
a problem, we could use the difference between the capabilities
QEMU_CAPS_BLOCKJOB_{ASYNC,SYNC} to determine whether we even
need snooping, and only request a modifying job in the case of
older qemu.

* src/qemu/qemu_driver.c (qemuDomainBlockJobImpl): Move info
handling...
(qemuDomainGetBlockJobInfo): ...here, and relax job type.
(qemuDomainBlockJobAbort, qemuDomainBlockJobSetSpeed)
(qemuDomainBlockRebase, qemuDomainBlockPull): Adjust callers.

Signed-off-by: Eric Blake <eblake@redhat.com>
2014-09-04 17:46:35 -06:00
.gnulib@2d280742a9 build: fix gnulib build for mingw 2014-07-09 16:09:17 -06:00
build-aux maint: improve syntax check for space around = 2014-08-12 11:21:17 -06:00
daemon maint: use consistent if-else braces in remaining spots 2014-09-04 14:34:03 -06:00
docs maint: tighten curly brace syntax checking 2014-09-04 15:38:00 -06:00
examples apparmor: allow reading cap_last_cap 2014-09-04 14:24:47 +02:00
gnulib maint: update to latest gnulib 2014-01-01 06:02:47 -07:00
include blockcopy: allow larger buf-size 2014-09-01 17:29:07 +02:00
m4 build: prefer -fstack-protector-strong to -all 2014-06-12 08:16:03 +02:00
po Release of libvirt-1.2.8 2014-09-02 09:41:09 +02:00
src blockjob: split out block info driver handling 2014-09-04 17:46:35 -06:00
tests maint: use hanging curly braces 2014-09-04 15:18:43 -06:00
tools maint: use consistent if-else braces in remaining spots 2014-09-04 14:34:03 -06:00
.ctags maint: Make ctags work out of the box 2013-07-18 08:47:21 +02:00
.dir-locals.el build: avoid tabs that failed syntax-check 2012-09-06 09:43:46 -06:00
.gitignore daemon: use socket activation with systemd 2014-08-22 09:12:14 +02:00
.gitmodules make .gnulib a submodule 2009-07-08 16:17:51 +02:00
.mailmap Autogenerate AUTHORS 2012-10-19 12:44:56 -04:00
AUTHORS.in Added myself in AUTHORS.in 2014-07-23 16:23:46 +02:00
autobuild.sh Disable libvirtd by default when building on Win32 2014-04-29 11:30:32 +01:00
autogen.sh maint: detect VPATH builds when checking for gnulib update 2014-06-04 16:06:55 -06:00
bootstrap maint: update to latest gnulib 2014-01-01 06:02:47 -07:00
bootstrap.conf Add helpers for getting env vars in a setuid environment 2013-10-21 14:03:52 +01:00
cfg.mk maint: tighten curly brace syntax checking 2014-09-04 15:38:00 -06:00
ChangeLog-old Fix typos in src/* 2014-04-21 16:49:08 -06:00
config-post.h build: fix build of virt-login-shell on systems with older gnutls 2013-10-22 09:41:50 -06:00
configure.ac Post-release version bump for new dev cycle 2014-09-02 10:07:15 +02:00
COPYING maint: follow recommended practice for using LGPL 2013-05-20 14:15:21 -06:00
COPYING.LESSER maint: follow recommended practice for using LGPL 2013-05-20 14:15:21 -06:00
HACKING maint: tighten curly brace syntax checking 2014-09-04 15:38:00 -06:00
libvirt-lxc.pc.in Add pkg-config files for libvirt-qemu & libvirt-lxc 2014-06-23 16:17:27 +01:00
libvirt-qemu.pc.in Add pkg-config files for libvirt-qemu & libvirt-lxc 2014-06-23 16:17:27 +01:00
libvirt.pc.in Add pkg-config files for libvirt-qemu & libvirt-lxc 2014-06-23 16:17:27 +01:00
libvirt.spec.in spec: Fix preun script for daemon 2014-09-03 11:56:38 +02:00
Makefile.am examples: Introduce domtop 2014-07-18 16:39:54 +02:00
Makefile.nonreentrant maint: use LGPL correctly 2013-05-20 14:03:48 -06:00
mingw-libvirt.spec.in build: package .pc files for mingw64 2014-07-09 16:45:15 -06:00
README
README-hacking docs: update README-hacking 2014-05-06 16:20:24 -06:00
run.in Add PKG_CONFIG_PATH to run.in script. 2014-06-26 14:32:35 +01:00
TODO Update todo list file to point at bugzilla/website 2010-10-13 16:45:26 +01:00

README 

         LibVirt : simple API for virtualization

  Libvirt is a C toolkit to interact with the virtualization capabilities
of recent versions of Linux (and other OSes). It is free software
available under the GNU Lesser General Public License. Virtualization of
the Linux Operating System means the ability to run multiple instances of
Operating Systems concurrently on a single hardware system where the basic
resources are driven by a Linux instance. The library aim at providing
long term stable C API initially for the Xen paravirtualization but
should be able to integrate other virtualization mechanisms if needed.

Daniel Veillard <veillard@redhat.com>