5c5df5310f
libxl can deliver events and invoke callbacks on any application thread calling into libxl. This can cause deadlock in the libvirt libxl driver Thread 19 (Thread 0x7f31411ec700 (LWP 14068) "libvirtd"): #0 0x00007f318520cc7d in __lll_lock_wait () from /lib64/libpthread.so.0 #1 0x00007f3185205ed5 in pthread_mutex_lock () from /lib64/libpthread.so.0 #2 0x00007f3189488015 in virMutexLock (m=<optimized out>) at ../../src/util/virthread.c:79 #3 0x00007f3189463f3b in virObjectLock (anyobj=<optimized out>) at ../../src/util/virobject.c:433 #4 0x00007f31894f2f41 in virDomainObjListSearchID (payload=0x7f317400a6d0, name=<optimized out>, data=0x7f31411eaeac) at ../../src/conf/virdomainobjlist.c:105 #5 0x00007f3189437ac5 in virHashSearch (ctable=0x7f3124025a30, iter=iter@entry=0x7f31894f2f30 <virDomainObjListSearchID>, data=data@entry=0x7f31411eaeac, name=name@entry=0x0) at ../../src/util/virhash.c:745 #6 0x00007f31894f3919 in virDomainObjListFindByID (doms=0x7f3124025430, id=<optimized out>) at ../../src/conf/virdomainobjlist.c:121 #7 0x00007f3152f292e5 in libxlDomainEventHandler (data=0x7f3124023d80, event=0x7f310c010ae0) at ../../src/libxl/libxl_domain.c:660 #8 0x00007f3152c6ff5d in egc_run_callbacks (egc=egc@entry=0x7f31411eaf50) at libxl_event.c:1427 #9 0x00007f3152c718bd in libxl__egc_cleanup (egc=0x7f31411eaf50) at libxl_event.c:1458 #10 libxl__ao_inprogress (ao=ao@entry=0x7f310c00b8a0, file=file@entry=0x7f3152cce987 "libxl_domain.c", line=line@entry=730, func=func@entry=0x7f3152ccf750 <__func__.22238> "libxl_domain_unpause") at libxl_event.c:2047 #11 0x00007f3152c8c5b8 in libxl_domain_unpause (ctx=0x7f3124015a40, domid=<optimized out>, ao_how=ao_how@entry=0x0) at libxl_domain.c:730 #12 0x00007f3152f2a584 in libxl_domain_unpause_0x041200 (domid=<optimized out>, ctx=<optimized out>) at /usr/include/libxl.h:1756 #13 libxlDomainStart (driver=driver@entry=0x7f3124023d80, vm=vm@entry=0x7f317400a6d0, start_paused=start_paused@entry=false, restore_fd=restore_fd@entry=-1, restore_ver=<optimized out>, restore_ver@entry=2) at ../../src/libxl/libxl_domain.c:1482 #14 0x00007f3152f2a6e3 in libxlDomainStartNew (driver=driver@entry=0x7f3124023d80, vm=vm@entry=0x7f317400a6d0, start_paused=start_paused@entry=false) at ../../src/libxl/libxl_domain.c:1545 #15 0x00007f3152f2a789 in libxlDomainShutdownHandleRestart (driver=0x7f3124023d80, vm=0x7f317400a6d0) at ../../src/libxl/libxl_domain.c:464 #16 0x00007f3152f2a9e4 in libxlDomainShutdownThread (opaque=<optimized out>) at ../../src/libxl/libxl_domain.c:559 #17 0x00007f3189487ee2 in virThreadHelper (data=<optimized out>) at ../../src/util/virthread.c:196 #18 0x00007f3185203539 in start_thread () from /lib64/libpthread.so.0 #19 0x00007f3184f3becf in clone () from /lib64/libc.so.6 Frame 16 runs a thread created to handle domain shutdown processing for domid 28712. In this case the event contained the reboot reason, so the old domain is destroyed and a new one is created by libxlDomainStart new. After starting the domain, it is unpaused by calling libxl_domain_unpause in frame 12. While the thread is running within libxl, libxl takes the opportunity to deliver a pending domain shutdown event for unrelated domid 28710. While searching for the associated virDomainObj by ID, a deadlock is encountered when attempting to lock the virDomainObj for domid 28712, which is already locked since this thread is processing its shutdown event. The deadlock can be avoided by moving the search for a virDomainObj associated with the event domid to the shutdown thread. The same is done for the death thread. Signed-off-by: Jim Fehlig <jfehlig@suse.com> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> Reviewed-by: Ján Tomko <jtomko@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 2.0 (or later). See the files COPYING.LESSER and COPYING for full license terms & conditions.
Installation
Instructions on building and installing libvirt can be found on the website:
https://libvirt.org/compiling.html
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: