On 11.12.2014 11:48, Martin Kletzander wrote:
When one domain is being undefined and at the same time started, for
example, there is a possibility of a rare problem occuring.
- Thread 1 does virDomainUndefine(), has the lock, checks that the
domain is active and because it's not, calls
virDomainObjListRemove().
- Thread 2 does virDomainCreate() and tries to lock the domain.
- Thread 1 needs to lock domain list in order to remove the domain from
it, but must unlock domain first (proper order is to lock domain list
first and the domain itself second).
- Thread 2 grabs the lock, starts the domain and releases the lock.
- Thread 1 grabs the lock and removes the domain from list.
With this patch:
- The undefining domain gets marked as "to undefine" before it is
unlocked.
- If domain is found in any of the search APIs, it's returned only if
it is not marked as "to undefine". The check is done while the
domain is locked.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1150505
Signed-off-by: Martin Kletzander <mkletzan@xxxxxxxxxx>
---
Notes:
I marked this as v3, but it is basically a resend of v1 [1] with
s/undefining/removing/ change. I'm sending this even though the second
version of the patch got in again because the v2 that we pushed didn't
help. I got convinced [2] that doing this with a job fixes it, but it
doesn't, it just serializes the Create API after the Undefine API. The
only difference that the commit b629c64e [3] does is that it waits on
obtaining job, but not on locking the domain. That previous commit can
be reverted if anyone wants, I see almost no point in it being there
now.
[1] http://www.redhat.com/archives/libvir-list/2014-October/msg01055.html
[2] http://www.redhat.com/archives/libvir-list/2014-October/msg01115.html
[3] http://libvirt.org/git/?p=libvirt.git;a=commitdiff;h=b629c64e
src/conf/domain_conf.c | 22 +++++++++++++++++++---
src/conf/domain_conf.h | 1 +
2 files changed, 20 insertions(+), 3 deletions(-)
ACK
Michal
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