[RFC PATCH v1 3/5] node_device_udev: Add comments about locking
Commit a99d876a0f58 ("node_device: Use automatic mutex management") replaced
the
locking mechanism and accidentally removed the comment with the reason why the
lock is taken. Restore this comment and add a new comment about the lock.
Note: If the comment is/was correct, then each caller of
`nodeDeviceUpdateMediatedDevices` must hold this lock.
Currently, that's not the case.
Signed-off-by: Marc Hartmayer <mhartmay(a)linux.ibm.com>
---
src/node_device/node_device_udev.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/src/node_device/node_device_udev.c b/src/node_device/node_device_udev.c
index 9f2abb9eb0dd..8b4a62537c06 100644
--- a/src/node_device/node_device_udev.c
+++ b/src/node_device/node_device_udev.c
@@ -72,8 +72,10 @@ struct _udevEventData {
/* init thread */
virThread *initThread;
- GList *mdevctlMonitors;
+ /* Protects @mdevctlMonitors and must be taken when `mdevctl` command is
+ * called to make sure only one thread can query mdevctl at a time. */
virMutex mdevctlLock;
+ GList *mdevctlMonitors;
int mdevctlTimeout;
};
@@ -2065,6 +2067,7 @@ static void
mdevctlUpdateThreadFunc(void *opaque G_GNUC_UNUSED)
{
udevEventData *priv = driver->privateData;
+ /* ensure only a single thread can query mdevctl at a time */
VIR_LOCK_GUARD lock = virLockGuardLock(&priv->mdevctlLock);
if (nodeDeviceUpdateMediatedDevices() < 0)
--
2.34.1