33c6eb9689
It is possible to deadlock libvirtd when concurrently starting a domain
and restarting the daemon. Threads involved in the deadlock are
Thread 4 (Thread 0x7fc13b53e700 (LWP 64084)):
/lib64/libpthread.so.0
at util/virthread.c:154
at qemu/qemu_monitor.c:1083
cmd=0x7fc110017700, scm_fd=-1, reply=0x7fc13b53d318) at
qemu/qemu_monitor_json.c:305
cmd=0x7fc110017700,
reply=0x7fc13b53d318) at qemu/qemu_monitor_json.c:335
at qemu/qemu_monitor_json.c:1298
at qemu/qemu_monitor.c:1697
vm=0x7fc110003d00, asyncJob=QEMU_ASYNC_JOB_START) at qemu/qemu_process.c:1763
vm=0x7fc110003d00,
asyncJob=6, logCtxt=0x7fc1100089c0) at qemu/qemu_process.c:1835
vm=0x7fc110003d00, asyncJob=6, logCtxt=0x7fc1100089c0) at
qemu/qemu_process.c:2180
driver=0x7fc12004e1e0,
vm=0x7fc110003d00, asyncJob=QEMU_ASYNC_JOB_START, incoming=0x0, snapshot=0x0,
vmop=VIR_NETDEV_VPORT_PROFILE_OP_CREATE, flags=17) at qemu/qemu_process.c:6111
driver=0x7fc12004e1e0,
vm=0x7fc110003d00, updatedCPU=0x0, asyncJob=QEMU_ASYNC_JOB_START,
migrateFrom=0x0,
migrateFd=-1, migratePath=0x0, snapshot=0x0,
vmop=VIR_NETDEV_VPORT_PROFILE_OP_CREATE,
flags=17) at qemu/qemu_process.c:6334
xml=0x7fc110000ed0 "<!--\nWARNING: THIS IS AN AUTO-GENERATED FILE.
CHANGES TO IT ARE LIKELY TO BE\nOVERWRITTEN AND LOST. Changes to this xml
configuration should be made using:\n virsh edit testvv\nor other
applicati"..., flags=0) at qemu/qemu_driver.c:1776
...
Thread 1 (Thread 0x7fc143c66880 (LWP 64081)):
/lib64/libpthread.so.0
at util/virthread.c:122
conf/nwfilter_conf.c:159
sig=0x7ffe0a831e30,
opaque=0x0) at remote/remote_daemon.c:724
opaque=0x558c5328b230) at rpc/virnetdaemon.c:654
at util/vireventpoll.c:508
rpc/virnetdaemon.c:858
remote/remote_daemon.c:1496
(gdb) thr 1
[Switching to thread 1 (Thread 0x7fc143c66880 (LWP 64081))]
/lib64/libpthread.so.0
(gdb) f 1
at util/virthread.c:122
122 pthread_rwlock_wrlock(&m->lock);
(gdb) p updateLock
$1 = {lock = {__data = {__lock = 0, __nr_readers = 1, __readers_wakeup = 0,
__writer_wakeup = 0, __nr_readers_queued = 0, __nr_writers_queued = 1,
__writer = 0,
__shared = 0, __rwelision = 0 '\000', __pad1 = "\000\000\000\000\000\000",
__pad2 = 0, __flags = 0},
__size = "\000\000\000\000\001", '\000' <repeats 15 times>, "\001",
'\000' <repeats 34 times>, __align = 4294967296}}
Reloading of the nwfilter driver is stuck waiting for a write lock, which
already has a reader (from qemuDomainCreateXML) in the critical section.
Since the reload occurs in the context of the main event loop thread,
libvirtd becomes deadlocked. The deadlock can be avoided by offloading
the reload work to a thread.
Signed-off-by: Jim Fehlig <jfehlig@suse.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Libvirt API for virtualization
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.
For some of these hypervisors, it provides a stateful management daemon which runs on the virtualization host allowing access to the API both by non-privileged local users and remote users.
Layered packages provide bindings of the libvirt C API into other languages including Python, Perl, PHP, Go, Java, OCaml, as well as mappings into object systems such as GObject, CIM and SNMP.
Further information about the libvirt project can be found on the website:
License
The libvirt C API is distributed under the terms of GNU Lesser General
Public License, version 2.1 (or later). Some parts of the code that are
not part of the C library may have the more restrictive GNU General
Public License, version 2.1 (or later). See the files COPYING.LESSER
and COPYING for full license terms & conditions.
Installation
Libvirt uses the GNU Autotools build system, so in general can be built and installed with the usual commands. For example, to build in a manner that is suitable for installing as root, use:
$ ./configure --prefix=/usr --sysconfdir=/etc --localstatedir=/var
$ make
$ sudo make install
While to build & install as an unprivileged user
$ ./configure --prefix=$HOME/usr
$ make
$ make install
The libvirt code relies on a large number of 3rd party libraries. These will
be detected during execution of the configure script and a summary printed
which lists any missing (optional) dependencies.
Contributing
The libvirt project welcomes contributions in many ways. For most components the best way to contribute is to send patches to the primary development mailing list. Further guidance on this can be found on the website:
https://libvirt.org/contribute.html
Contact
The libvirt project has two primary mailing lists:
- libvirt-users@redhat.com (for user discussions)
- libvir-list@redhat.com (for development only)
Further details on contacting the project are available on the website: