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sched/semaphore: fix priority boost restoration for priority inheritance

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Signed-off-by: Petro Karashchenko <petro.karashchenko@gmail.com>
This commit is contained in:
Petro Karashchenko
2022-10-03 15:14:24 -03:00
committed by Alan Carvalho de Assis
parent 03bce705d5
commit d247e8d1d2
8 changed files with 87 additions and 395 deletions
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Documentation/reference/user/05_counting_semaphore.rst
-17
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@@ -77,23 +77,6 @@ implementation:
slightly increased code size and around 6-12 bytes times the value of
``CONFIG_SEM_PREALLOCHOLDERS``.
- ``CONFIG_SEM_NNESTPRIO``: In addition, there may be multiple
threads of various priorities that need to wait for a count from the
semaphore. These, the lower priority thread holding the semaphore may
have to be boosted numerous times and, to make things more complex,
will have to keep track of all of the boost priorities values in
order to correctly restore the priorities after a count has been
handed out to the higher priority thread. The
``CONFIG_SEM_NNESTPRIO`` defines the size of an array, one array per
active thread. This setting is the maximum number of higher priority
threads (minus 1) than can be waiting for another thread to release a
count on a semaphore. This value may be set to zero if no more than
one thread is expected to wait for a semaphore.
The cost associated with setting ``CONFIG_SEM_NNESTPRIO`` is slightly
increased code size and (``CONFIG_SEM_PREALLOCHOLDERS`` + 1) times
the maximum number of active threads.
- **Increased Susceptibility to Bad Thread Behavior**. These various
structures tie the semaphore implementation more tightly to the
behavior of the implementation. For examples, if a thread executes