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Commit 5da98b82 authored by Mauro Carvalho Chehab's avatar Mauro Carvalho Chehab Committed by Jonathan Corbet
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pi-futex.txt: standardize document format 



Each text file under Documentation follows a different
format. Some doesn't even have titles!

Change its representation to follow the adopted standard,
using ReST markups for it to be parseable by Sphinx.

This document requires just minor adjustments to match
the standard documentation style:

- promote document name;
- remove extra collons on some chapter titles;
- use "-" for a bulleted list.

Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: default avatarJonathan Corbet <corbet@lwn.net>
parent 5426a2cc

Documentation/pi-futex.txt

+8 −7
Original line number Diff line number Diff line 
======================

Lightweight PI-futexes

----------------------

======================



We are calling them lightweight for 3 reasons:
@@ -25,8 +26,8 @@ determinism and well-bound latencies. Even in the worst-case, PI will 
improve the statistical distribution of locking related application

delays.



The longer reply:

-----------------

The longer reply

----------------



Firstly, sharing locks between multiple tasks is a common programming

technique that often cannot be replaced with lockless algorithms. As we
@@ -71,8 +72,8 @@ deterministic execution of the high-prio task: any medium-priority task 
could preempt the low-prio task while it holds the shared lock and

executes the critical section, and could delay it indefinitely.



Implementation:

---------------

Implementation

--------------



As mentioned before, the userspace fastpath of PI-enabled pthread

mutexes involves no kernel work at all - they behave quite similarly to
@@ -83,8 +84,8 @@ entering the kernel. 


To handle the slowpath, we have added two new futex ops:



  FUTEX_LOCK_PI

  FUTEX_UNLOCK_PI

  - FUTEX_LOCK_PI

  - FUTEX_UNLOCK_PI



If the lock-acquire fastpath fails, [i.e. an atomic transition from 0 to

TID fails], then FUTEX_LOCK_PI is called. The kernel does all the