A common event flag cluster is a set of 32 event
flags that enable cooperating processes to post event notifications
to each other.
Event flags in the cluster can be set or cleared
to indicate the occurrence of an event. All event flags are contained
within clusters of 32 event flags, and each process has access to
four clusters (numbered 0 through 3). Two of the clusters are local
to a single process. Event flag clusters 2 and 3 are called common
event flag clusters and are used for interprocess synchronization.
A subject may be associated with up to two common event flag clusters.
Each common event flag in a cluster is referenced by an event flag
The name of the object is whatever character string
was supplied as an argument to the Associate Common Event Flag Cluster
system service ($ASCEFC). Remember that common event flag cluster
names are qualified by your UIC group number.
Types of Access
The common event flag cluster class supports the
following types of access:
Gives a process
the right to establish an association with the named cluster so the
process can access event flags.
Gives a process the right to mark a permanent event
flag cluster for deletion with the Delete Common Event Flag Cluster
($DLCEFC) system service. The actual deletion occurs once all processes
disassociate from the cluster.
Gives you the right to modify the protection elements
of the common event flag cluster.
The common event flag cluster class provides one
template profile. Although the template assigns an owner UIC of [0,0],
this value is only temporary. As soon as the object is created, the
operating system replaces a 0 value with the value in the corresponding
field of the creating process's UIC.
| Template Name|| Owner UIC|| Protection Code|
When the process creating the common event flag
cluster supplies a prot argument
to $ASCEFC that has a value of 1, then the system modifies the template
so the process UIC is the owner, and the protection code denies group
Creation of a permanent common event flag cluster
requires the PRMCEB privilege. This privilege also grants delete access
for permanent clusters.
Kinds of Auditing Performed
The system can audit the following types of events:
| Event Audited|| When Audit Occurs|
When the first process to associate with a particular
cluster calls $ASCEFC
Whenever subsequent callers to $ASCEFC associate with the cluster
When a process calls $DACEFC or associates with another
cluster or at image rundown
process calls $DLCEFC
Permanence of the Object
A common event flag cluster and its security profile
need to be reset each time a system starts up.