Priority Inheritance Protocols

Sha, L., Rajkumar, R., & Lehoczky, J. P. (1990). Priority Inheritance Protocols: An Approach to Real-Time Synchronization. IEEE, 39(9), 1175-1185.

Type

Journal article

Intellectual base

Primary research

Year

1990

Volume

39

Issue

9

Pages

1175-1185

DOI

10.1109/12.57058

DOI registrant

Institute of Electrical and Electronics Engineers

Link

https://doi.org/10.1109/12.57058

Cited from

psychology

Cited by

7 citations across 7 artifacts.

Each citation links to the sentence it supports in the citing article.

Primes

• Goal Shielding
  • In operating systems and concurrency the transfer is sharp: a thread holding a lock during a critical section is goal-shielded — other threads run but are inhibited from the claimed resources until lock release — and the priority-inversion failure mode is a textbook goal-shielding failure where an insufficiently inhibited alternative steals resources from a higher-priority goal.

    This sourceDefines unbounded priority inversion (a thread holding a lock blocks a higher-priority task while a medium task preempts) and the priority-inheritance fix that raises the lock-holder's priority so it completes and releases.

    Supported in partVerified against the publisher's abstract

    The paper's own abstract confirms unbounded priority inversion as a real blocking problem that priority inheritance protocols solve, but it says nothing about goal shielding or about other threads running while the holder is shielded.

    “Both protocols solve the uncontrolled priority inversion problem.”

    Read by an automated reader; not a human review. How support was checked

Mechanisms

• Blocked Item Escalation
  • Real-time systems formalize the idea as the priority-inheritance protocol: a task blocked on a resource held by a lower-priority task lends it priority so the blocker finishes and releases sooner.

    This sourceDefines priority inheritance: when a higher-priority task blocks on a resource held by a lower-priority task, the holder temporarily inherits the higher priority so it can finish its critical section and release the resource.

• Mutex or Lock
  • Two locks acquired in inconsistent orders can also wait on each other forever, and a low-priority holder can stall a high-priority waiter

    This sourceDefines priority inversion as higher-priority work being blocked by lower-priority work.

• Priority-Band Triage Rule
  • A low band can be starved indefinitely — priority inversion and outright starvation are the classic hazards, where a high-priority item is blocked behind, or a low-priority need is never served because higher demand never lets up.

    This sourceDefines uncontrolled priority inversion as a higher-priority job being blocked by lower-priority work for an indefinite period.

• Priority Bypass Token
  • The subtler one is priority inversion,

    This sourceDefines priority inversion as a high-priority task being blocked by a lower-priority task that holds a shared resource.

• Priority Queue
  • A subtler technical hazard is priority inversion, in which a high-priority item is effectively blocked by a low-priority one that holds a needed resource, so the ranking fails to deliver the response it promises.

    This sourceDefines priority inversion as the blocking of a higher-priority job by lower-priority work that controls a needed synchronization resource.

• Shared-Bus Arbitration Protocol
  • Its failure mode is the flip side of strict priority: low-priority traffic can be starved indefinitely on a busy bus, and worse, a high-priority message can end up blocked behind a low-priority one that already holds the bus — the classic priority inversion trap.

    This sourceDefines priority inversion as a higher-priority job being blocked by a lower-priority job that already controls a required shared resource.

Verification

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