Whenever we get the RESUME event from QEMU, we change the state of the
affected domain to VIR_DOMAIN_RUNNING with VIR_DOMAIN_RUNNING_UNPAUSED
reason. This is fine if the domain is resumed unexpectedly, but when we
sent "cont" to QEMU we usually have a better reason for the state
change. The better reason is used in qemuProcessStartCPUs which also
sets the domain state to running if qemuMonitorStartCPUs reports
success. Thus we may end up with two state updates in a row, but the
final reason is correct.
This patch is a preparation for dropping the state change done in
qemuMonitorStartCPUs for which we need to pass the actual running reason
to the RESUME event handler and use it there instead of
VIR_DOMAIN_RUNNING_UNPAUSED.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>
This patch replaces some rather generic VIR_DOMAIN_RUNNING_UNPAUSED
reasons when changing domain state to running with more specific ones.
All of them are done when libvirtd reconnects to an existing domain
after being restarted and sees an unfinished migration or save.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>
VIR_DOMAIN_EVENT_RESUMED_FROM_SNAPSHOT was defined but not used anywhere
in our event generation code. This fixes qemuDomainRevertToSnapshot to
properly report why the domain was resumed.
Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>
A deadlock situation can occur when autostarting a LXC domain 'guest'
due to two threads attempting to take opposing locks while holding
opposing locks (AB BA problem). Thread A takes and holds the 'vm' lock
while attempting to take the 'client' lock, meanwhile, thread B takes
and holds the 'client' lock while attempting to take the 'vm' lock.
The potential for this can be seen as follows:
Thread A:
virLXCProcessAutostartDomain (takes vm lock)
--> virLXCProcessStart
--> virLXCProcessConnectMonitor
--> virLXCMonitorNew
--> virNetClientSetCloseCallback (wants client lock)
Thread B:
virNetClientIncomingEvent (takes client lock)
--> virNetClientIOHandleInput
--> virNetClientCallDispatch
--> virNetClientCallDispatchMessage
--> virNetClientProgramDispatch
--> virLXCMonitorHandleEventInit
--> virLXCProcessMonitorInitNotify (wants vm lock)
Since these threads are scheduled independently and are preemptible it
is possible for the deadlock scenario to occur where each thread locks
their first lock but both will fail to get their second lock and just
spin forever. You get something like:
virLXCProcessAutostartDomain (takes vm lock)
--> virLXCProcessStart
--> virLXCProcessConnectMonitor
--> virLXCMonitorNew
<...>
virNetClientIncomingEvent (takes client lock)
--> virNetClientIOHandleInput
--> virNetClientCallDispatch
--> virNetClientCallDispatchMessage
--> virNetClientProgramDispatch
--> virLXCMonitorHandleEventInit
--> virLXCProcessMonitorInitNotify (wants vm lock but spins)
<...>
--> virNetClientSetCloseCallback (wants client lock but spins)
Neither thread ever gets the lock it needs to be able to continue
while holding the lock that the other thread needs.
The actual window for preemption which can cause this deadlock is
rather small, between the calls to virNetClientProgramNew() and
execution of virNetClientSetCloseCallback(), both in
virLXCMonitorNew(). But it can be seen in real world use that this
small window is enough.
By moving the call to virNetClientSetCloseCallback() ahead of
virNetClientProgramNew() we can close any possible chance of the
deadlock taking place. There should be no other implications to the
move since the close callback (in the unlikely event was called) will
spin on the vm lock. The remaining work that takes place between the
old call location of virNetClientSetCloseCallback() and the new
location is unaffected by the move.
Signed-off-by: Mark Asselstine <mark.asselstine@windriver.com>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
With the introduction of cgroup v2 there are new names used with
cgroups based on which version is used:
- legacy: cgroup v1
- unified: cgroup v2
- hybrid: cgroup v1 and cgroup v2
Let's use 'legacy' instead of 'cgroupv1' or 'controllers' in our code.
Reviewed-by: Fabiano Fidêncio <fidencio@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
They all need virCgroupV1GetMemoryUnlimitedKB() so it's easier to
move them in one commit.
Reviewed-by: Fabiano Fidêncio <fidencio@redhat.com>
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
We need to update one test-case because now new cgroup object will be
created only if there is any cgroup backend available.
Reviewed-by: Ján Tomko <jtomko@redhat.com>
Signed-off-by: Pavel Hrdina <phrdina@redhat.com>
