GDSX Manual

Design and Development
Extended General Device Support (GDSX) Manual–134303
2-32
Checkpointing
2. The task’s stack image and TCB are placed at the next available word in the
checkpoint buffer. (Global data may have previously been queued in the buffer.)
3. The checkpoint buffer is written to brother.
4. The semaphore cpsem is released.
When the backup process receives the checkpoint message, any global data included is
copied to the same address in the backup. The checkpointing task’s stack image is
copied to an extended memory area of size specified by the TASKSIZE configuration
parameter. The backup copies the checkpointed portion of the TCB to the appropriate
location in the TCB pool.
Type 2 Checkpoint
A call to ^CHECKPOINT(2) checkpoints all local and extended memory pool buffers
acquired by the calling task. If USCODE has allocated an extended segment (with an ID
in the range from 0 to 1023) through calls to ALLOCATESEGMENT and
USESEGMENT, such a segment is not checkpointed with a call to ^CHECKPOINT(2).
When a task does a type 2 checkpoint, the following actions occur. Note that before
CHECKPOINT(2) is called by a task, global data may have been put in the checkpoint
buffer by call(s) to Q^CP[X].
1. The semaphore cpsem is acquired.
2. All memory pools are searched and all areas owned by the task are copied into the
extended memory area with address tcb.buffers.
The format of this area is:
Each pool image is formatted as:
The last pool entry is a dummy and has a size of zero.
3. The area just constructed is moved to the next available word in the checkpoint
buffer. (Global data may have previously been queued in the buffer.)
4. The task’s stack image and TCB are placed in the checkpoint buffer.
5. The checkpoint buffer is written to brother.
6. The semaphore cpsem is released.
cpbuffer.size Total size of the checkpoint record
cpbuffer.task Task number of checkpointer
cpbuffer.data Buffer pool images
size Size of checkpointed data
xaddr Address of data in the primary buffer pool
data Buffer pool data image