# Priority inheritance > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Priority_inheritance > Markdown URL: https://mediated.wiki/source/Priority_inheritance.md > Source: https://en.wikipedia.org/wiki/Priority_inheritance > Source revision: 1330220234 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{Short description|Computer programming method}}In [real-time computing](/source/real-time_computing), '''priority inheritance''' is a method for eliminating unbounded [priority inversion](/source/priority_inversion). Using this [programming](/source/Computer_programming) method, a [process scheduling](/source/process_scheduling) [algorithm](/source/algorithm) increases the priority of a process (A) to the maximum priority of any other process waiting for any [resource](/source/resource_(computer_science)) on which A has a [resource lock](/source/Lock_(computer_science)) (if it is higher than the original priority of A). The basic idea of the priority inheritance protocol is that when a job blocks one or more high-priority jobs, it ignores its original priority assignment and executes its [critical section](/source/critical_section) at an elevated priority level. After executing its critical section and releasing its locks, the process returns to its original priority level. ==Example== Consider three jobs: {| class="wikitable" |- ! Job Name ! Priority |- | H | High |- | M | Medium |- | L | Low |} Suppose that both H and L require some shared resource. If L acquires this shared resource (entering a critical section), and H subsequently requires it, H will block until L releases it (leaving its critical section). Without priority inheritance, process M could [preempt](/source/Preemption_(computing)) process L during the critical section and delay its completion, in effect causing the lower-priority process M to indirectly preempt the high-priority process H. This is a [priority inversion](/source/priority_inversion) bug. With priority inheritance, L will execute its critical section at H's high priority whenever H is blocked on the shared resource. As a result, M will be unable to preempt L and will be blocked. That is, the higher-priority job M must wait for the critical section of the lower priority job L to be executed, because L has inherited H's priority. When L exits its critical section, it regains its original (low) priority and awakens H (which was blocked by L). H, having high priority, preempts L and runs to completion. This enables M and L to resume in succession and run to completion without priority inversion. ==Operating systems supporting priority inheritance== *[Windows](/source/Microsoft_Windows){{cite web|url=https://learn.microsoft.com/en-us/windows/win32/procthread/priority-inversion|title=Priority Inversion|publisher=[Microsoft](/source/Microsoft)|access-date=30 December 2025}} *[Linux](/source/Linux){{cite web | url = https://www.kernel.org/doc/html/v5.15/locking/rt-mutex.html | title = RT-mutex subsystem with PI support | access-date = 2021-11-27 }} *[ERIKA Enterprise](/source/ERIKA_Enterprise) *[FreeRTOS](/source/FreeRTOS) *[Eclipse ThreadX](/source/Eclipse_ThreadX) *[VxWorks](/source/VxWorks) *[iRMX](/source/iRMX){{Cite web |url=https://apps.dtic.mil/sti/tr/pdf/ADA408745.pdf#page=7 |title=Resource-centric real-time kernel and middleware services |page=3 |accessdate=2024-01-01}} ==See also== *[Priority ceiling protocol](/source/Priority_ceiling_protocol) ==References== * {{cite journal |author1=Lui Sha |author2=Ragunathan Rajkumar |author3=John P. Lehoczky |name-list-style=amp |date=September 1990 | title = Priority Inheritance Protocols: An Approach to Real-Time Synchronization | journal = [IEEE Transactions on Computers](/source/IEEE_Transactions_on_Computers) | volume = 39 | issue = 9 | pages = 1175–1185 | url = https://www.csie.ntu.edu.tw/~r95093/papers/Priority%20Inheritance%20Protocols%20An%20Approach%20to%20Real-Time%20Synchronization.pdf | doi = 10.1109/12.57058 |archive-url=https://web.archive.org/web/20220419175141/https://www.csie.ntu.edu.tw/~r95093/papers/Priority%20Inheritance%20Protocols%20An%20Approach%20to%20Real-Time%20Synchronization.pdf |archive-date=2022-04-19 }} {{reflist}} ==External links== * "[https://web.archive.org/web/20070706071045/http://www.linuxdevices.com/articles/AT5698775833.html Priority Inheritance: The Real Story]" by [Doug Locke](/source/Doug_Locke) * "[https://web.archive.org/web/20070706071207/http://www.linuxdevices.com/articles/AT7168794919.html Against Priority Inheritance]" by [Victor Yodaiken](/source/Victor_Yodaiken) * "[http://rtdoc.cs.uri.edu/downloads/wohlever_thesis.pdf Implementing Concurrency Control With Priority Inheritance in Real-Time CORBA]" by [Steven Wohlever](/source/Steven_Wohlever), [Victor Fay Wolfe](/source/Victor_Fay_Wolfe) and Russell Johnston * "[http://citeseer.ist.psu.edu/108383.html Priority Inheritance Spin Locks for Multiprocessor Real-Time Systems]" by [Cai-Dong Wang](/source/Cai-Dong_Wang), [Hiroaki Takada](/source/Hiroaki_Takada) and [Ken Sakamura](/source/Ken_Sakamura) * "[http://doi.ieeecomputersociety.org/10.1109/REAL.2003.1253271 Hardware Support for Priority Inheritance]" by [Bilge E. S. Akgul](/source/Bilge_E._S._Akgul), [Vincent J. Mooney](/source/Vincent_J._Mooney), [Henrik Thane](/source/Henrik_Thane) and [Pramote Kuacharoen](/source/Pramote_Kuacharoen) Category:Real-time computing Category:Concurrency control {{compu-sci-stub}} --- Adapted from the Wikipedia article [Priority inheritance](https://en.wikipedia.org/wiki/Priority_inheritance) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Priority_inheritance?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.