8:36 a.m.
This is a significant rework of v1 as
- patch 1 was dropped because an equivalent change was accidentally committed
in the meantime in 4c53267b70fc5c548b6530113c3f96870d8d7fc1
- patch 2 was dropped as it was just a mostly formal clean-up of patch 1
- patch 3 was redone using a different approach.
Patch 3 now takes the approach that was hinted at in the last paragraph of
v1's cover letter, more specifically it now fixes qemuProcessStop() rather
than its caller. Digging into git history I located the commit that
introduced qemuProcessStop()'s problematic behaviour and after consulting with
Michal, we agreed that fixing qemuProcessStop() seems safe enough, and
definitely a better solution conceptually.
Pavel Mores (1):
qemu: fix concurrency crash bug in snapshot revert
src/qemu/qemu_domain.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
--
2.21.0
8:36 a.m.
New subject: [libvirt] [PATCH v2 1/1] qemu: fix concurrency crash bug in snapshot revert
This commit aims to fix
https://bugzilla.redhat.com/show_bug.cgi?id=1610207
The cause was apparently incorrect handling of jobs in snapshot revert code
which allowed a thread executing snapshot delete to begin job while
snapshot revert was still running on another thread. The snapshot delete
thread then waited on a condition variable in qemuMonitorSend() while the
revert thread finished, changing (and effectively corrupting) the
qemuMonitor structure under the delete thread which led to its crash.
The incorrect handling of jobs in revert code was due to the fact that
although qemuDomainRevertToSnapshot() correctly begins a job at the start,
the job was implicitly ended when qemuProcessStop() was called because the
job lives in the QEMU driver's private data (qemuDomainObjPrivate) that
was purged during qemuProcessStop().
This fix prevents qemuProcessStop() from clearing jobs as the idea of
qemuProcessStop() clearing jobs seems wrong in the first place. It was
(inadvertently) introduced in commit 888aa4b6b9db65e3db273341e79846, which
is effectively reverted by the second hunk of this commit. To preserve
the desired effects of the faulty commit, the first hunk is included as
suggested by Michal.
Signed-off-by: Pavel Mores <pmores(a)redhat.com>
---
src/qemu/qemu_domain.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
index 6f53e17b6a..e4a1bccc18 100644
--- a/src/qemu/qemu_domain.c
+++ b/src/qemu/qemu_domain.c
@@ -403,6 +403,8 @@ qemuDomainObjRestoreJob(virDomainObjPtr obj,
static void
qemuDomainObjFreeJob(qemuDomainObjPrivatePtr priv)
{
+ qemuDomainObjResetJob(priv);
+ qemuDomainObjResetAsyncJob(priv);
VIR_FREE(priv->job.current);
VIR_FREE(priv->job.completed);
virCondDestroy(&priv->job.cond);
@@ -2161,9 +2163,6 @@ qemuDomainObjPrivateDataClear(qemuDomainObjPrivatePtr priv)
virBitmapFree(priv->migrationCaps);
priv->migrationCaps = NULL;
- qemuDomainObjResetJob(priv);
- qemuDomainObjResetAsyncJob(priv);
-
virHashRemoveAll(priv->blockjobs);
virHashRemoveAll(priv->dbusVMStates);
--
2.21.0
3:41 a.m.
New subject: [libvirt] [PATCH v2 1/1] qemu: fix concurrency crash bug in snapshot revert
On 12/10/19 11:36 AM, Pavel Mores wrote:
This commit aims to fix
https://bugzilla.redhat.com/show_bug.cgi?id=1610207
The cause was apparently incorrect handling of jobs in snapshot revert code
which allowed a thread executing snapshot delete to begin job while
snapshot revert was still running on another thread. The snapshot delete
thread then waited on a condition variable in qemuMonitorSend() while the
revert thread finished, changing (and effectively corrupting) the
qemuMonitor structure under the delete thread which led to its crash.
The incorrect handling of jobs in revert code was due to the fact that
although qemuDomainRevertToSnapshot() correctly begins a job at the start,
the job was implicitly ended when qemuProcessStop() was called because the
job lives in the QEMU driver's private data (qemuDomainObjPrivate) that
was purged during qemuProcessStop().
This fix prevents qemuProcessStop() from clearing jobs as the idea of
qemuProcessStop() clearing jobs seems wrong in the first place. It was
(inadvertently) introduced in commit 888aa4b6b9db65e3db273341e79846, which
is effectively reverted by the second hunk of this commit. To preserve
the desired effects of the faulty commit, the first hunk is included as
suggested by Michal.
Signed-off-by: Pavel Mores <pmores(a)redhat.com>
---
Reviewed-by: Daniel Henrique Barboza <danielhb413(a)gmail.com>
4:32 a.m.
New subject: [libvirt] [PATCH v2 1/1] qemu: fix concurrency crash bug in snapshot revert
On 12/10/19 3:36 PM, Pavel Mores wrote:
This commit aims to fix
https://bugzilla.redhat.com/show_bug.cgi?id=1610207
The cause was apparently incorrect handling of jobs in snapshot revert code
which allowed a thread executing snapshot delete to begin job while
snapshot revert was still running on another thread. The snapshot delete
thread then waited on a condition variable in qemuMonitorSend() while the
revert thread finished, changing (and effectively corrupting) the
qemuMonitor structure under the delete thread which led to its crash.
The incorrect handling of jobs in revert code was due to the fact that
although qemuDomainRevertToSnapshot() correctly begins a job at the start,
the job was implicitly ended when qemuProcessStop() was called because the
job lives in the QEMU driver's private data (qemuDomainObjPrivate) that
was purged during qemuProcessStop().
This fix prevents qemuProcessStop() from clearing jobs as the idea of
qemuProcessStop() clearing jobs seems wrong in the first place. It was
(inadvertently) introduced in commit 888aa4b6b9db65e3db273341e79846, which
is effectively reverted by the second hunk of this commit. To preserve
the desired effects of the faulty commit, the first hunk is included as
suggested by Michal.
Signed-off-by: Pavel Mores <pmores(a)redhat.com>
---
src/qemu/qemu_domain.c | 5 ++---
1 file changed, 2 insertions(+), 3 deletions(-)
Reviewed-by: Michal Privoznik <mprivozn(a)redhat.com>
Michal
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days inactive
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3 comments
3 participants
participants (3)
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Daniel Henrique Barboza -
Michal Privoznik -
Pavel Mores