language agnostic - Are there any cases where priority inheritance is not desirable? -

i understand priority inheritance is. understand, mars pathfinder's system reset issue, of time, depending upon criticality of operation, enable/implement priority inheritance.

however, there cases priority inheritance not desirable , may cause problems if enabled/implemented? if so, please provide example while preferably describing problem?

op gives example priority inheritance desirable. there have short mutex-protected transaction between threads of highest , lowest priorities , long-running thread medium priority block transaction if priority inheritance not used. in example high-priority thread more important application medium-priority thread.

to priority inheritance not desirable, make application these assumptions opposite above example. let's make transaction between threads of highest , lowest priorities longer time available medium-priority thread perform task. , let's assume results of medium-priority thread more important results of high-priority thread.

imagine application should serve 100 interrupts per second high-priority thread. , 10 interrupts per second medium-priority thread (where each interrupt needs 30 ms processed). low-priority thread lock resource (used high-priority thread). , (very rarely) lock long time (1 sec). priority inheritance first access resource high-priority thread boosts priority of background thread 1 sec. medium-priority thread miss 10 interrupts. @ same time high-priority thread miss 100 interrupts. without priority inheritance medium-priority thread serves interrupts high-priority thread misses 130 interrupts. if interrupts served medium-priority thread more valuable, should prefer disable priority inheritance.

i never seen real-life application this. invented 1 illustrate case. let video capture application computer vision task in background , (as additional bonus) sound recording. video frames captured medium-priority thread. sound captured high-priority thread (because otherwise video capturing process block significant portion of sound interrupts). video captured pre-allocated buffer. audio captured silence suppression (no memory needed capture silence). audio thread needs dynamically allocated memory blocks (this our shared resource). computer vision task allocates memory blocks. when out-of-memory, garbage collector thread blocks memory allocation , work. here without priority inheritance video capture works flawlessly. priority inheritance audio thread blocks video capture (which considered bad application).

---

also there applications priority inheritance not give benefits:

• when there (1) several background threads , (2) several short-living priority threads. each group of threads shares resources inside own group.
• when 1 resource shared threads priorities 1 & 2, other 1 - threads priorities 3 & 4, etc.
• when processor has more cores there time-critical threads in application.
• in many other cases.

if priority inheritance enabled in such cases, performance (or power efficiency) degradation because priority inheritance implementation in kernel needs additional resources.