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Long ago I incorrectly associated libxl fd and timer registrations with per-domain libxl_ctx objects. When creating a libxlDomainObjPrivate, a libxl_ctx is allocated, and libxl_osevent_register_hooks is called passing a pointer to the libxlDomainObjPrivate. When an fd or timer registration occurred, the registration callback received the libxlDomainObjPrivate, containing the per-domain libxl_ctx. This libxl_ctx was then used when informing libxl about fd events or timer expirations. The problem with this approach is that fd and timer registrations do not share the same lifespan as libxlDomainObjPrivate, and hence the per-domain libxl_ctx ojects. The result is races between per-domain libxl_ctx's being destoryed and events firing on associated fds/timers, typically manifesting as an assert in libxl libxl_internal.h:2788: libxl__ctx_unlock: Assertion `!r' failed There is no need to associate libxlDomainObjPrivate objects with libxl's desire to use libvirt's event loop. Instead, the driver-wide libxl_ctx can be used for the fd and timer registrations. This patch moves the fd and timer handling code away from the domain-specific code in libxl_domain.c into libxl_driver.c. While at it, function names were changed a bit to better describe their purpose. The unnecessary locking was also removed since the code simply provides a wrapper over the event loop interface. Indeed the locks may have been causing some deadlocks when repeatedly creating/destroying muliple domains. There have also been rumors about such deadlocks during parallel OpenStack Tempest runs. Signed-off-by: Jim Fehlig <jfehlig@suse.com>
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>