Re: [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&gt; --- 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)