Task Management Readiness table and ready lease

Task Readiness Table

The ready state flags for each task are placed in the ready table, with two variables osrdygrp and osrdytbl[] in the Ready table.

In Osrdygrp, tasks are grouped by priority, with 8 tasks as a group. Each of the OSRDYGRP indicates whether there are tasks in each group in the 8-group task that have entered the ready state. When the task enters the ready state, the corresponding bit of the corresponding element in the Ready table osrdytbl[] is also placed.

N assuming that the priority 12 task is in the ready state, 12=1100b, then osrdytbl[1] 4th position 1, and the 1th position of the Osrdygrp 1, the corresponding mathematical expression is:

Osrdygrp |=0x02;

OSRDYTBL[1] |=0x10;

N and the Priority 21 task is ready 21=10 101b, then osrdytbl[2] 5th position 1, and osrdygrp 2nd position 1, the corresponding mathematical expression is:

Osrdygrp |=0x04;

OSRDYTBL[2] |=0x20;

N from the above calculation: if Osrdygrp and osrdybbl[] the nth position 1, it should be the value of OSRDYGRP and osrdybbl[] and 2n phase or. In Uc/os, the 8 values of the 2n n=0-7 are calculated first in the presence array osmaptbl[7], i.e.:

Osmaptbl[0] = = 0x01 (0000 0001)

OSMAPTBL[1] = 0x02 (0000 0010)

......

OSMAPTBL[7] = 0x80 (1000 0000)

N if Prio is the priority of the task, that is, the task's identification number, the task is placed in the ready table, even if the task enters the ready state by:

Osrdygrp |= osmaptbl[prio>>3];

OSRDYTBL[PRIO>>3] |= osmaptbl[prio&0x07];

N Assuming priority is 12--1100b

Osrdygrp |=0x02;

OSRDYTBL[1] |=0x10;

n zeroing the corresponding bits of the corresponding element in the task-ready table osrdytbl[prio>>3], and when all the bits in osrdytbl[prio>>3] are zero, that is, when none of the tasks in the group of the task is in the Ready state, The corresponding bit of the OSRDYGRP is zero.

if ((Osrdytbl[prio>>3] &=

~OSMAPTBL[PRIO&0X07]) = = 0)

Osrdygrp &= ~osmaptbl[prio>>3];

Determine the highest priority based on the readiness table

Two key points:

The priority series is decomposed into high three-bit and low three-bit respectively.

High priority has a small priority number;

Task Management Readiness table and ready lease