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 4.4.3.3. PSL Procedure for AFU-Directed Programming Models

Each PSL assigned to service the scheduled processes is configured with a unique identifier and the identifier of the next PSL in the list of PSLs servicing the processes. In addition, each PSL is identified as either the first PSL, the last PSL, both first and last PSL (only one PSL servicing the queue), or neither first or last PSL. The PSL ID Register contains the PSL unique identifier and the settings for first and last.

 Operations Performed by the First PSL (PSL_ID[L,F] = '01')

When the terminate_element MMIO command is received by the first PSL, the PSL checks to see if the process element being terminated is currently running. It performs any operations necessary, and sends the terminate_element command to the next PSL.

  1. The PSL notifies the AFU of the process element termination. The AFU performs any necessary operations to remove the process and then acknowledges the termination of the process element. When the acknowledgment is received, the PSL continues with the next substep.

  2. If the process is running, the process is terminated. The AFU and PSL are allowed to complete any outstanding transactions but should not start any new transactions for the process.

  3. The PSL writes a termination command to the psl_chained_command doubleword for the next PSL.

    • Write the value (x'00010000' || next_psl_id || link_of_element_to_terminate) to the psl_chained_command.

  Operations Performed by the Next PSL (PSL_ID[L,F] = '00')

When the terminate_element command is detected by the next PSL, the PSL checks to see if the process element being terminated is currently running. It performs any operations necessary, and sends the terminate_element command to the next PSL. The terminate_element command is detected by monitoring the psl_chained_command doubleword.

  1. The PSL notifies the AFU of the process element termination. The AFU performs any necessary operations to remove the process and then acknowledges the termination of the process element. When the acknowledgment is received, the PSL continues with the next substep.

  2. If the process is running, the process is terminated. The AFU and PSL are allowed to complete any outstanding transactions but should not start any new transactions for the process.

  3. The PSL writes a termination command to the psl_chained_command doubleword for the next PSL and watches for the termination to be complete.

    • Write the value (x'00010000' || next_psl_id || link_of_element_to_terminate) to the psl_chained_command.

 Operations Performed by the Last PSL (PSL_ID[L] = '1')

When the terminate_element MMIO command is received or the terminate_element command is detected by the last PSL, the PSL checks to see if the process element that is being terminated is currently running. It performs any operations necessary, and sets the completion status in the software command/status word. The terminate_element command is detected by monitoring the psl_chained_command doubleword.

  1. The PSL notifies the AFU of the process element termination. The AFU performs any necessary operations to remove the process and then acknowledges the termination of the process element. When the acknowledgment is received, the PSL continues with the next substep.

  2. If the process is running, the process is terminated. The AFU and PSL are allowed to complete any outstanding transactions but should not start any new transactions for the process.

  3. The PSL sets the completion status in the software command/status field to indicate that the process has been successfully terminated.

    • The status field in sw_command_status is set to x'0001' using a caching-inhibited DMA or special memory-update operation that is guaranteed not to corrupt memory if the operation fails. The final value of sw_command_status should be (x'00010001' || first_psl_id || link_of_element_to_terminate).


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