blob: 8a095266d8f6bfc67dd00dd9d5553fc1dec1b81e (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
|
This test exposes a potential priority inversion when priority inheritance is
used and multiple locks are acquired by a low priority task. The scenario
consists of 2 tasks of different priority and 2 semaphore/mutexes using
priority inheritance. The scenario is:
Task 1 has priority 36. Task 2 has priority 34.
1. Task 1 obtains semaphore S1.
2. Task 1 obtains semaphore S2
3. Task 2 preempts Task 1.
4. Task 2 blocks on S2. Task 1 inherits priority 34.
5. Task 1 resumes. Task 1 releases S2. Task 1 continues to run at priority 34.
6. Task 1 releases S1. Task 1 changes priority back to 36.
7. Task 2 now preempts Task 1 and begins operating again.
During steps 5-6 Task 1 executes when Task 2 should be able to execute.
Stepping down the priority of Task 1 when it releases S2 back to its original
priority when it obtained S2 fixes the priority inversion.
|
