Portal ==>> AutoSAR Practical series 300 speak 「 candy Autosar」 General catalogue

1 Priority reversal

Be careful ： In this section T1 Have the highest priority ,T4 With lowest priority .
As shown in the figure below , When a higher priority task is forced to wait indefinitely for a lower priority task to complete , There will be priority reversal .

When a lower priority task T4 Hold higher priority tasks T1 Required resources , That may be the case . Mission T1 As long as the resource cannot be obtained, it will not enter the running state . When T1 When holding this resource , This resource is not available but , Any priority between T1 and T4 If the task between does not request access to resources , Can preempt T4 .T1 You will see an unlimited number of low priority tasks running , meanwhile T4 Occupancy resources .

2 Priority ceiling protocol

Be careful ： The resources in this section have the highest priority ,T3 second ,T1 With lowest priority .
OSEK Prevent this by imposing a priority ceiling protocol on its resource management . The priority ceiling protocol is calculated according to the following rules ：