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From 0e943a1b117ea13b530236f94a0bc22a831eefeb Mon Sep 17 00:00:00 2001
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Message-Id: <0e943a1b117ea13b530236f94a0bc22a831eefeb@dist-git>
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From: Martin Kletzander <mkletzan@redhat.com>
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Date: Tue, 4 Nov 2014 11:02:52 +0100
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Subject: [PATCH] qemu: avoid rare race when undefining domain
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When one domain is being undefined and at the same time started, for
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example, there is a possibility of a rare problem occuring.
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- Thread 1 does virDomainUndefine(), has the lock, checks that the
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domain is active and because it's not, calls
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virDomainObjListRemove().
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- Thread 2 does virDomainCreate() and tries to lock the domain.
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- Thread 1 needs to lock domain list in order to remove the domain from
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it, but must unlock domain first (proper order is to lock domain list
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first and the domain itself second).
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- Thread 2 grabs the lock, starts the domain and releases the lock.
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- Thread 1 grabs the lock and removes the domain from list.
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With this patch:
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- qemuDomainRemoveInactive() creates a QEMU_JOB_MODIFY if that's
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possible, but since it must remove the domain from list either way,
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it continues even when starting the job failed.
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Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1150505
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Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
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(cherry picked from commit b629c64e5e0a32ef439b8eeb3a697e2cd76f3248)
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Signed-off-by: Martin Kletzander <mkletzan@redhat.com>
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Signed-off-by: Jiri Denemark <jdenemar@redhat.com>
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---
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src/qemu/qemu_domain.c | 7 +++++++
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1 file changed, 7 insertions(+)
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diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
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index 72d7279..d166269 100644
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--- a/src/qemu/qemu_domain.c
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+++ b/src/qemu/qemu_domain.c
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@@ -2391,9 +2391,13 @@ void
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qemuDomainRemoveInactive(virQEMUDriverPtr driver,
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virDomainObjPtr vm)
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{
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+ bool haveJob = true;
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char *snapDir;
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virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver);
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+ if (qemuDomainObjBeginJob(driver, vm, QEMU_JOB_MODIFY) < 0)
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+ haveJob = false;
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+
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/* Remove any snapshot metadata prior to removing the domain */
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if (qemuDomainSnapshotDiscardAllMetadata(driver, vm) < 0) {
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VIR_WARN("unable to remove all snapshots for domain %s",
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@@ -2410,6 +2414,9 @@ qemuDomainRemoveInactive(virQEMUDriverPtr driver,
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}
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virDomainObjListRemove(driver->domains, vm);
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virObjectUnref(cfg);
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+
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+ if (haveJob)
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+ ignore_value(qemuDomainObjEndJob(driver, vm));
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}
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void
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--
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2.1.3
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