feat: add lab-rv32i-freertos-scheduler-states card
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# K04 — Scheduler states, priorities, time slicing and typed ticks
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## Position in the series
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- Series: FreeRTOS C++
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- Lesson: L03, card K04
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- Duration: 30 minutes
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- Executables: exactly one
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- Kernel: unchanged FreeRTOS V11.3.0 in C
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- C++ mode: freestanding C++17, no exceptions, RTTI or hosted `libstdc++`
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- New C++ surface: `Ticks`, `TickPoint`, non-owning `TaskRef`
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K02 introduced task entry and lifecycle, while K03 established ownership and
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RAII for a heap buffer. K04 deliberately does not build a large facade. It
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first exposes the scheduler's raw evidence and adds only types that prevent a
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duration, a tick point and an owning task object from being confused.
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## Outcome
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After 30 minutes the student can predict and verify `READY`, `RUNNING`,
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`BLOCKED` and `DELETED`; distinguish a relative delay from a periodic wake
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reference; explain time slicing for equal priorities; and use the order
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`BEFORE -> HIGH -> AFTER` as proof of immediate priority preemption.
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## Lesson plan — 30 minutes
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| Time | Mode | Required evidence |
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| --- | --- | --- |
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| 0–4 | prediction | fill the first state/priority table without running code |
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| 4–8 | typed time | distinguish `Ticks` from `TickPoint`; no assumption that tick means ms |
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| 8–13 | time slicing | obtain `A,B,A` or `B,A,B` at equal priority 2 |
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| 13–19 | blocked state | show A=`eBlocked`, B=`eRunning`, elapsed exactly 3 ticks |
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| 19–25 | priority change | show B at priority 3 and marker order `1,2,3` |
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| 25–30 | interpretation | compare relative/periodic delay, state limits and stale `TaskRef` |
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## Canonical experiment
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```text
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scheduler starts
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-> startup probe: A READY, B READY
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-> equal priority 2: A/B alternate on tick boundaries
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-> A calls vTaskDelay(3)
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-> A BLOCKED; B RUNNING
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-> at start+3 A becomes READY and then RUNNING
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-> A writes BEFORE=1 and raises B to priority 3
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-> B preempts, writes HIGH=2, lowers itself to priority 2
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-> A resumes inside/after vTaskPrioritySet and writes AFTER=3
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-> workers delete themselves; verifier writes terminal snapshot and PASS
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```
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The test accepts either initial equal-priority order. It requires the
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alternating relation `first == third && first != second`.
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## Stable evidence contract
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| Evidence | Required relation |
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| --- | --- |
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| `g_alternating_tasks[0..2]` | A,B,A or B,A,B |
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| delay snapshot | A=`eBlocked`, B=`eRunning` |
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| delay timestamps | `end - start == 3`, observation lies before end |
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| priority snapshot | A=`eReady`, B=`eRunning`, B priority 3 |
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| `g_priority_order` | exactly `1,2,3` |
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| terminal snapshot | A/B recorded as `eDeleted`, handles no longer queried |
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| `g_scheduler_states_pass` | 1 |
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## Prediction table
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The student completes state and priority before inspecting the executable:
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| Event | A state / priority | B state / priority | Current task | Why? |
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| --- | --- | --- | --- | --- |
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| startup probe | | | | |
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| A before delay | | | | |
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| B while A delays | | | | |
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| A after 3 ticks | | | | |
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| before raise | | | | |
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| B at p=3 | | | | |
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| after API returns | | | | |
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| verifier | | | | |
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## Typed wrapper boundary
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```cpp
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freertos::Ticks duration{3};
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const auto start = freertos::TickPoint::now();
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vTaskDelay(duration.count());
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const auto elapsed = freertos::TickPoint::now() - start;
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freertos::TaskRef peer{handle}; // no ownership
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peer.set_priority(3);
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```
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`TaskRef` is the size of one native handle and has no virtual dispatch. It
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must not be used after the task is deleted. K04 uses raw scheduling calls on
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purpose; a broad `Scheduler` facade is deferred until K09.
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## Misconceptions to surface
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1. Highest priority does not mean “always running”: a high-priority task can
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be blocked and therefore ineligible.
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2. `vTaskDelay(3)` does not promise three milliseconds unless the configured
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tick rate makes that conversion true.
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3. `vTaskDelay` is relative; repeated work plus relative delays can drift.
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`xTaskDelayUntil` advances a periodic reference.
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4. Equal priority does not establish a fixed first task; verify alternation,
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not a guessed first ID.
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5. A handle is not ownership. After deletion, `TaskRef` can dangle.
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## Acceptance
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- host test proves typed tick arithmetic, wrap-around and one-handle `TaskRef`;
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- ELF contains no RTTI, vtable, exception/unwind or hosted C++ dependency;
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- Hazard3 proves a three-entry alternating trace;
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- the blocked snapshot and exactly-three-tick delay pass;
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- priority markers are exactly `1,2,3` and B is priority 3 at marker 2;
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- all eight snapshots match the intended state transition sequence;
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- student explains why the startup snapshot is taken after scheduler start.
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\hspace*{0.28em}\textcolor{orange!85!black}{EK~LOCAL~DBG.SCHED}\textcolor{black!48}{\pdftooltip[width=\textwidth]{.01}{Koreluje snapshoty, ticki i kolejność wykonania z decyzjami kernela.}}\par%
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\hspace*{0.54em}\textcolor{blue!70!black}{KW~LOCAL~DBG.SCHED}\textcolor{black!48}{\pdftooltip[width=\textwidth]{.01}{Pokazuje X,Y,X; elapsed=3; A BLOCKED; B/p3 oraz porządek 1,2,3.}}\par%
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\hspace*{0.00em}\textcolor{red}{WE~01}\textcolor{black!48}{}\par%
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\hspace*{0.28em}\textcolor{green!50!black}{EN~LOCAL~EN~RTOS.MODEL}\textcolor{black!48}{\pdftooltip[width=\textwidth]{.01}{Analizuje gotowość, stan, priorytet i jednostkę czasu.}}\par%
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\hspace*{0.54em}\textcolor{blue!70!black}{KW~LOCAL~KW~RTOS.MODEL}\textcolor{black!48}{\pdftooltip[width=\textwidth]{.01}{Wyjaśnia BLOCKED mimo wysokiego priorytetu oraz relative delay kontra periodic reference.}}\par%
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\end{minipage}%
|
||||
}%
|
||||
\end{minipage}%
|
||||
}
|
||||
|
||||
}
|
||||
|
||||
\begin{document}
|
||||
\sloppy
|
||||
|
||||
\vspace{1.0em}
|
||||
\noindent{\Large\bfseries Cel karty}\par
|
||||
\vspace{0.35em}
|
||||
Uczeń przewiduje i odtwarza stany dwóch tasków, mierzy blokadę w tickach i dowodzi natychmiastowego wywłaszczenia porządkiem BEFORE--HIGH--AFTER.
|
||||
|
||||
\vspace{0.8em}
|
||||
\noindent\textcolor{black!25}{\rule{\textwidth}{0.35pt}}
|
||||
\vspace{0.7em}
|
||||
\noindent{\Large\bfseries Zakres karty}\par
|
||||
\vspace{0.35em}
|
||||
Jedno zadanie uruchamia prawdziwy scheduler FreeRTOS na Hazard3. Warstwa C++ dodaje tylko typy \texttt{Ticks}, \texttt{TickPoint} oraz nieposiadający \texttt{TaskRef}; pełna fasada schedulera i własność taska są poza zakresem.
|
||||
|
||||
\vspace{0.8em}
|
||||
\noindent\textcolor{black!25}{\rule{\textwidth}{0.35pt}}
|
||||
|
||||
\clearpage
|
||||
|
||||
\ESCSectionBlockStart
|
||||
\section{Stan i gotowość do wykonania}
|
||||
\reversemarginpar
|
||||
\marginnote[%
|
||||
\begin{minipage}{\marginparwidth}%
|
||||
\raggedright
|
||||
{\fontsize{3.55}{3.95}\selectfont\ttfamily
|
||||
\begin{minipage}[t]{\marginparwidth}%
|
||||
\raggedright
|
||||
{\bfseries\textcolor{black!65}{TECH}\par}%
|
||||
\vspace{0.08em}%
|
||||
\hspace*{0.00em}\textcolor{red}{WE~01}\textcolor{black!48}{}\par%
|
||||
\end{minipage}%
|
||||
}%
|
||||
\end{minipage}%
|
||||
]{}[-3.1em]
|
||||
\normalmarginpar
|
||||
|
||||
\marginnote{%
|
||||
\begin{minipage}{\marginparwidth}%
|
||||
\raggedright
|
||||
{\fontsize{3.55}{3.95}\selectfont\ttfamily
|
||||
\hspace*{0.06cm}%
|
||||
\begin{minipage}[t]{\dimexpr\marginparwidth-0.06cm\relax}%
|
||||
\raggedright
|
||||
{\bfseries\textcolor{black!65}{OG}\par}%
|
||||
\vspace{0.08em}%
|
||||
\hspace*{0.00em}\textcolor{red}{WE~01}\textcolor{black!48}{}\par%
|
||||
\end{minipage}%
|
||||
}%
|
||||
\end{minipage}%
|
||||
}[-3.1em]
|
||||
|
||||
|
||||
\begingroup
|
||||
\scriptsize\ttfamily\color{black!60}\sloppy
|
||||
\noindent drzewka: \pdftooltip[width=\textwidth]{D1}{K04.WE01.OG.LOCAL.RTOS.MODEL.01 | WE 01: Stany, priorytety i ticki. Przewidzenie i\textCR udowodnienie decyzji schedulera FreeRTOS. | EN LOCAL RTOS.MODEL.01: Analizuje gotowość,\textCR stan, priorytet i jednostkę czasu. | KW LOCAL RTOS.MODEL.01: Wyjaśnia BLOCKED mimo wysokiego\textCR priorytetu oraz relative delay kontra periodic reference.}\par
|
||||
\vspace{0.10em}%
|
||||
\noindent K1: Wypełnij tabelę stanów przed uruchomieniem kodu.\quad D1\par
|
||||
\ESCTinyStepSeparator
|
||||
\noindent K2: Wyjaśnij, dlaczego BLOCKED/p4 przegrywa z READY/p2.\quad D1\par
|
||||
\par\vspace{0.18em}%
|
||||
\endgroup
|
||||
|
||||
Zadanie o najwyższym priorytecie wygrywa tylko wtedy, gdy jest gotowe. Przewidź READY, RUNNING, BLOCKED i DELETED w ośmiu punktach.
|
||||
\ESCSectionBlockEnd
|
||||
|
||||
\ESCSectionBlockStart
|
||||
\section{Time slicing i blokada na trzy ticki}
|
||||
\reversemarginpar
|
||||
\marginnote[%
|
||||
\begin{minipage}{\marginparwidth}%
|
||||
\raggedright
|
||||
{\fontsize{3.55}{3.95}\selectfont\ttfamily
|
||||
\begin{minipage}[t]{\marginparwidth}%
|
||||
\raggedright
|
||||
{\bfseries\textcolor{black!65}{TECH}\par}%
|
||||
\vspace{0.08em}%
|
||||
\hspace*{0.00em}\textcolor{red}{WE~01}\textcolor{black!48}{}\par%
|
||||
\end{minipage}%
|
||||
}%
|
||||
\end{minipage}%
|
||||
]{}[-3.1em]
|
||||
\normalmarginpar
|
||||
|
||||
\marginnote{%
|
||||
\begin{minipage}{\marginparwidth}%
|
||||
\raggedright
|
||||
{\fontsize{3.55}{3.95}\selectfont\ttfamily
|
||||
\hspace*{0.06cm}%
|
||||
\begin{minipage}[t]{\dimexpr\marginparwidth-0.06cm\relax}%
|
||||
\raggedright
|
||||
{\bfseries\textcolor{black!65}{OG}\par}%
|
||||
\vspace{0.08em}%
|
||||
\hspace*{0.00em}\textcolor{red}{WE~01}\textcolor{black!48}{}\par%
|
||||
\end{minipage}%
|
||||
}%
|
||||
\end{minipage}%
|
||||
}[-3.1em]
|
||||
|
||||
|
||||
\begingroup
|
||||
\scriptsize\ttfamily\color{black!60}\sloppy
|
||||
\noindent drzewka: \pdftooltip[width=\textwidth]{D1}{K04.WE01.TECH.LOCAL.DBG.SCHED.01 | WE 01: Stany, priorytety i ticki. Przewidzenie i\textCR udowodnienie decyzji schedulera FreeRTOS. | EK LOCAL DBG.SCHED.01: Koreluje snapshoty, ticki\textCR i kolejność wykonania z decyzjami kernela. | KW LOCAL DBG.SCHED.01: Pokazuje X,Y,X;\textCR elapsed=3; A BLOCKED; B/p3 oraz porządek 1,2,3.}\par
|
||||
\vspace{0.10em}%
|
||||
\noindent K1: Sprawdź relację first==third i first!=second.\quad D1\par
|
||||
\ESCTinyStepSeparator
|
||||
\noindent K2: Zapisz snapshot BLOCKED/RUNNING oraz trzy ticki elapsed.\quad D1\par
|
||||
\par\vspace{0.18em}%
|
||||
\endgroup
|
||||
|
||||
Dopuść A--B--A albo B--A--B, a następnie pokaż A jako BLOCKED i różnicę end-start równą 3 ticki.
|
||||
\ESCSectionBlockEnd
|
||||
|
||||
\ESCSectionBlockStart
|
||||
\section{Natychmiastowe wywłaszczenie po zmianie priorytetu}
|
||||
\reversemarginpar
|
||||
\marginnote[%
|
||||
\begin{minipage}{\marginparwidth}%
|
||||
\raggedright
|
||||
{\fontsize{3.55}{3.95}\selectfont\ttfamily
|
||||
\begin{minipage}[t]{\marginparwidth}%
|
||||
\raggedright
|
||||
{\bfseries\textcolor{black!65}{TECH}\par}%
|
||||
\vspace{0.08em}%
|
||||
\hspace*{0.00em}\textcolor{red}{WE~01}\textcolor{black!48}{}\par%
|
||||
\end{minipage}%
|
||||
}%
|
||||
\end{minipage}%
|
||||
]{}[-3.1em]
|
||||
\normalmarginpar
|
||||
|
||||
\marginnote{%
|
||||
\begin{minipage}{\marginparwidth}%
|
||||
\raggedright
|
||||
{\fontsize{3.55}{3.95}\selectfont\ttfamily
|
||||
\hspace*{0.06cm}%
|
||||
\begin{minipage}[t]{\dimexpr\marginparwidth-0.06cm\relax}%
|
||||
\raggedright
|
||||
{\bfseries\textcolor{black!65}{OG}\par}%
|
||||
\vspace{0.08em}%
|
||||
\hspace*{0.00em}\textcolor{red}{WE~01}\textcolor{black!48}{}\par%
|
||||
\end{minipage}%
|
||||
}%
|
||||
\end{minipage}%
|
||||
}[-3.1em]
|
||||
|
||||
|
||||
\begingroup
|
||||
\scriptsize\ttfamily\color{black!60}\sloppy
|
||||
\noindent drzewka: \pdftooltip[width=\textwidth]{D1}{K04.WE01.TECH.LOCAL.DBG.SCHED.01 | WE 01: Stany, priorytety i ticki. Przewidzenie i\textCR udowodnienie decyzji schedulera FreeRTOS. | EK LOCAL DBG.SCHED.01: Koreluje snapshoty, ticki\textCR i kolejność wykonania z decyzjami kernela. | KW LOCAL DBG.SCHED.01: Pokazuje X,Y,X;\textCR elapsed=3; A BLOCKED; B/p3 oraz porządek 1,2,3.}\par
|
||||
\vspace{0.10em}%
|
||||
\noindent K1: Pokaż B jako RUNNING/p3, gdy A jest READY/p2.\quad D1\par
|
||||
\ESCTinyStepSeparator
|
||||
\noindent K2: Udowodnij porządek markerów 1,2,3.\quad D1\par
|
||||
\par\vspace{0.18em}%
|
||||
\endgroup
|
||||
|
||||
A zapisuje BEFORE=1, podnosi B do p3 i dopiero po wznowieniu zapisuje AFTER=3. B musi zapisać HIGH=2 pomiędzy nimi.
|
||||
\ESCSectionBlockEnd
|
||||
|
||||
\ESCSectionBlockStart
|
||||
\section{Typy i granica nieposiadającej referencji}
|
||||
\reversemarginpar
|
||||
\marginnote[%
|
||||
\begin{minipage}{\marginparwidth}%
|
||||
\raggedright
|
||||
{\fontsize{3.55}{3.95}\selectfont\ttfamily
|
||||
\begin{minipage}[t]{\marginparwidth}%
|
||||
\raggedright
|
||||
{\bfseries\textcolor{black!65}{TECH}\par}%
|
||||
\vspace{0.08em}%
|
||||
\hspace*{0.00em}\textcolor{red}{WE~01}\textcolor{black!48}{}\par%
|
||||
\end{minipage}%
|
||||
}%
|
||||
\end{minipage}%
|
||||
]{}[-3.1em]
|
||||
\normalmarginpar
|
||||
|
||||
\marginnote{%
|
||||
\begin{minipage}{\marginparwidth}%
|
||||
\raggedright
|
||||
{\fontsize{3.55}{3.95}\selectfont\ttfamily
|
||||
\hspace*{0.06cm}%
|
||||
\begin{minipage}[t]{\dimexpr\marginparwidth-0.06cm\relax}%
|
||||
\raggedright
|
||||
{\bfseries\textcolor{black!65}{OG}\par}%
|
||||
\vspace{0.08em}%
|
||||
\hspace*{0.00em}\textcolor{red}{WE~01}\textcolor{black!48}{}\par%
|
||||
\end{minipage}%
|
||||
}%
|
||||
\end{minipage}%
|
||||
}[-3.1em]
|
||||
|
||||
|
||||
\begingroup
|
||||
\scriptsize\ttfamily\color{black!60}\sloppy
|
||||
\noindent drzewka: \pdftooltip[width=\textwidth]{D1}{K04.WE01.OG.LOCAL.RTOS.MODEL.01 | WE 01: Stany, priorytety i ticki. Przewidzenie i\textCR udowodnienie decyzji schedulera FreeRTOS. | EN LOCAL RTOS.MODEL.01: Analizuje gotowość,\textCR stan, priorytet i jednostkę czasu. | KW LOCAL RTOS.MODEL.01: Wyjaśnia BLOCKED mimo wysokiego\textCR priorytetu oraz relative delay kontra periodic reference.}\par
|
||||
\vspace{0.10em}%
|
||||
\noindent K1: Porównaj vTaskDelay z xTaskDelayUntil.\quad D1\par
|
||||
\ESCTinyStepSeparator
|
||||
\noindent K2: Uzasadnij brak odczytu przez TaskRef po delete.\quad D1\par
|
||||
\par\vspace{0.18em}%
|
||||
\endgroup
|
||||
|
||||
Ticks opisuje czas trwania, TickPoint punkt licznika, a TaskRef tylko widok uchwytu. Po usunięciu taska widok może wisieć.
|
||||
\ESCSectionBlockEnd
|
||||
|
||||
\end{document}
|
||||
+284
@@ -0,0 +1,284 @@
|
||||
\documentclass[10pt]{article}
|
||||
\usepackage[T1]{fontenc}
|
||||
\usepackage[utf8]{inputenc}
|
||||
\usepackage[polish]{babel}
|
||||
\usepackage[a4paper,margin=1.55cm]{geometry}
|
||||
\usepackage{array,tabularx,booktabs}
|
||||
\usepackage{amsmath,amssymb}
|
||||
\usepackage{xcolor,listings}
|
||||
\usepackage{hyperref,fancyhdr,lastpage,enumitem}
|
||||
|
||||
\definecolor{accent}{HTML}{16324A}
|
||||
\definecolor{accentlight}{HTML}{EEF3F7}
|
||||
\definecolor{rulegray}{HTML}{D7DEE5}
|
||||
\hypersetup{colorlinks=true,linkcolor=accent,urlcolor=blue}
|
||||
\IfFileExists{build-meta.tex}{\input{build-meta.tex}}{\newcommand{\BuildCommit}{local}}
|
||||
\newcommand{\PublisherDomain}{mpabi}
|
||||
\newcommand{\CardArea}{inf}
|
||||
\newcommand{\CardSeries}{freertos-cpp}
|
||||
\newcommand{\CardNumber}{04}
|
||||
\newcommand{\CardCount}{16}
|
||||
\newcommand{\CardSlug}{scheduler-states}
|
||||
\newcommand{\CardVersion}{v00.01}
|
||||
\newcommand{\DocumentUUID}{853a7dd7-b00b-4f4a-96e8-c160fc5bb04a}
|
||||
\newcommand{\blank}[1]{\rule{#1}{.2pt}}
|
||||
|
||||
\lstset{
|
||||
language=C++,basicstyle=\ttfamily\scriptsize,columns=fullflexible,
|
||||
keepspaces=true,frame=single,breaklines=true,showstringspaces=false,
|
||||
numbers=none,backgroundcolor=\color{accentlight},rulecolor=\color{rulegray}
|
||||
}
|
||||
\pagestyle{fancy}
|
||||
\fancyhf{}
|
||||
\lhead{\textbf{K04 · FreeRTOS C++ · scheduler}}
|
||||
\rhead{\small L03 · stany, priorytety, ticki}
|
||||
\lfoot{\scriptsize commit \BuildCommit}
|
||||
\cfoot{\scriptsize \thepage/\pageref{LastPage}}
|
||||
\rfoot{\scriptsize V11.3.0 / \CardVersion}
|
||||
\setlength{\headheight}{14pt}
|
||||
\setlength{\footskip}{19pt}
|
||||
\setlist[itemize]{nosep,leftmargin=1.45em}
|
||||
\setlist[enumerate]{nosep,leftmargin=1.65em}
|
||||
|
||||
\begin{document}
|
||||
\sloppy
|
||||
|
||||
\begin{center}
|
||||
{\LARGE\bfseries Scheduler: stany, priorytety i typowane ticki}\par
|
||||
\vspace{.25em}
|
||||
{\large przewidź przełączenie, potem udowodnij je śladem}\par
|
||||
\end{center}
|
||||
|
||||
\noindent\begin{tabularx}{\textwidth}{@{}p{1.65cm}Xp{1.55cm}X@{}}
|
||||
\toprule
|
||||
Karta & K04 / \CardCount & Czas & 30 minut \\
|
||||
Platforma & Hazard3 / RV32I & Język & freestanding C++17 \\
|
||||
Scheduler & preemption + time slicing & Kernel & V11.3.0, bez zmian \\
|
||||
Wersja & \CardVersion & UUID karty & \texttt{853a7dd7-...} \\
|
||||
\bottomrule
|
||||
\end{tabularx}
|
||||
|
||||
\section*{Cel i jedna sekwencja dowodowa}
|
||||
|
||||
Dwa zadania A i B mają priorytet 2. Najpierw scheduler dzieli CPU między
|
||||
równych. Potem A blokuje się na 3 ticki. Na końcu A podnosi priorytet B do 3.
|
||||
Nie zgadujemy kolejności --- zapisujemy stany, ticki oraz znaczniki wykonania.
|
||||
|
||||
\begin{center}
|
||||
\texttt{READY} $\rightarrow$ \texttt{RUNNING} $\rightarrow$
|
||||
\texttt{BLOCKED} $\rightarrow$ \texttt{READY} $\rightarrow$
|
||||
\texttt{RUNNING} $\rightarrow$ \texttt{DELETED}
|
||||
\end{center}
|
||||
|
||||
\noindent\fcolorbox{accent}{accentlight}{%
|
||||
\begin{minipage}{.94\textwidth}
|
||||
\textbf{Dwa warunki K04.} Zadanie o najwyższym priorytecie wygrywa tylko wtedy,
|
||||
gdy jest gotowe. Tick jest jednostką schedulera, nie ukrytą nazwą milisekundy.
|
||||
\end{minipage}}
|
||||
|
||||
\section*{Plan 30 minut}
|
||||
|
||||
\begin{tabularx}{\textwidth}{@{}p{1.35cm}p{3.0cm}X@{}}
|
||||
\toprule
|
||||
Czas & Tryb & Dowód ucznia \\
|
||||
\midrule
|
||||
0--4 & predykcja & tabela stanów i bieżącego zadania \\
|
||||
4--8 & czas typowany & \texttt{Ticks} kontra \texttt{TickPoint} \\
|
||||
8--13 & time slicing & A--B--A albo B--A--B przy priorytecie 2 \\
|
||||
13--19 & blokada & A=BLOCKED, B=RUNNING, różnica ticków 3 \\
|
||||
19--25 & priorytet & BEFORE--HIGH--AFTER ma wartości 1--2--3 \\
|
||||
25--30 & wyjście & delay względny/okresowy i granica \texttt{TaskRef} \\
|
||||
\bottomrule
|
||||
\end{tabularx}
|
||||
|
||||
\section*{Najpierw przewidź}
|
||||
|
||||
Który identyfikator pojawi się pierwszy: A czy B? \blank{2cm}\quad
|
||||
Czy test powinien wymagać właśnie tej odpowiedzi? \blank{5cm}
|
||||
|
||||
\newpage
|
||||
\section{Stany są warunkiem kwalifikacji do CPU}
|
||||
|
||||
\begin{tabularx}{\textwidth}{@{}p{2.5cm}p{4.0cm}X@{}}
|
||||
\toprule
|
||||
Stan & Czy może teraz dostać CPU? & Typowa przyczyna \\
|
||||
\midrule
|
||||
\texttt{eRunning} & tak, jedno zadanie na rdzeń & scheduler właśnie je wybrał \\
|
||||
\texttt{eReady} & tak, czeka na wybór & równy/niższy priorytet lub wywłaszczenie \\
|
||||
\texttt{eBlocked} & nie & delay albo oczekiwanie na zdarzenie \\
|
||||
\texttt{eSuspended} & nie & jawne zawieszenie, nie upływ czasu \\
|
||||
\texttt{eDeleted} & nie & stan terminalny w śladzie tej karty \\
|
||||
\bottomrule
|
||||
\end{tabularx}
|
||||
|
||||
\subsection*{Pułapka „najwyższy zawsze działa”}
|
||||
|
||||
Jeżeli A ma priorytet 4, ale jest \texttt{BLOCKED}, a B ma priorytet 2 i jest
|
||||
\texttt{READY}, scheduler wybierze \blank{2cm}, ponieważ
|
||||
\blank{10cm}.
|
||||
|
||||
\subsection*{Równe priorytety i time slicing}
|
||||
|
||||
Przy \texttt{configUSE\_PREEMPTION=1} oraz
|
||||
\texttt{configUSE\_TIME\_SLICING=1} tick może przenieść wykonanie do innego
|
||||
gotowego zadania o tym samym priorytecie. Zalicza relacja:
|
||||
|
||||
\begin{center}
|
||||
\texttt{first == third \&\& first != second}
|
||||
\end{center}
|
||||
|
||||
Wpisz dwa dopuszczalne ślady: \blank{3cm}\quad lub \quad\blank{3cm}.
|
||||
|
||||
\section{Czas: wartość ma znaczenie dopiero z jednostką}
|
||||
|
||||
\begin{lstlisting}
|
||||
freertos::Ticks duration{3};
|
||||
const auto start = freertos::TickPoint::now();
|
||||
vTaskDelay(duration.count());
|
||||
const auto elapsed = freertos::TickPoint::now() - start;
|
||||
\end{lstlisting}
|
||||
|
||||
\texttt{Ticks} jest czasem trwania. \texttt{TickPoint} jest punktem na
|
||||
zawijającym się liczniku. Odejmowanie dwóch punktów daje czas trwania także
|
||||
przy przejściu licznika przez maksimum typu bez znaku.
|
||||
|
||||
\noindent\begin{tabularx}{\textwidth}{@{}p{4.4cm}X@{}}
|
||||
\toprule
|
||||
API & Znaczenie \\
|
||||
\midrule
|
||||
\texttt{vTaskDelay(3)} & blokada względna: trzy ticki od chwili wywołania \\
|
||||
\texttt{xTaskDelayUntil} (\texttt{\&next,3}) & kolejny termin względem zapamiętanej osi okresu \\
|
||||
\bottomrule
|
||||
\end{tabularx}
|
||||
|
||||
W laboratorium tick rate wynosi 1000 Hz, ale poprawne zdanie brzmi
|
||||
„A było zablokowane przez \blank{1.5cm} ticki”. Przeliczenie na ms:
|
||||
\blank{3cm}. Co zmieni się przy 250 Hz? \blank{5cm}
|
||||
|
||||
\newpage
|
||||
\section{Tabela predykcji i obserwacji}
|
||||
|
||||
Najpierw wypełnij kolumnę „predykcja”. Dopiero potem uruchom program i wpisz
|
||||
wartości z \texttt{g\_snapshots}. Priorytet zapisuj obok stanu, np.
|
||||
\texttt{READY/p2}.
|
||||
|
||||
\renewcommand{\arraystretch}{1.32}
|
||||
\noindent\begin{tabularx}{\textwidth}{@{}p{.7cm}p{2.3cm}p{3.2cm}p{3.2cm}p{1.8cm}X@{}}
|
||||
\toprule
|
||||
Nr & Zdarzenie & A: pred./odczyt & B: pred./odczyt & Current & Dlaczego? \\
|
||||
\midrule
|
||||
1 & startup & \blank{2.7cm} & \blank{2.7cm} & \blank{1.3cm} & \blank{2.05cm} \\
|
||||
2 & przed delay & \blank{2.7cm} & \blank{2.7cm} & \blank{1.3cm} & \blank{2.05cm} \\
|
||||
3 & A czeka & \blank{2.7cm} & \blank{2.7cm} & \blank{1.3cm} & \blank{2.05cm} \\
|
||||
4 & A obudzone & \blank{2.7cm} & \blank{2.7cm} & \blank{1.3cm} & \blank{2.05cm} \\
|
||||
5 & BEFORE & \blank{2.7cm} & \blank{2.7cm} & \blank{1.3cm} & \blank{2.05cm} \\
|
||||
6 & HIGH & \blank{2.7cm} & \blank{2.7cm} & \blank{1.3cm} & \blank{2.05cm} \\
|
||||
7 & AFTER & \blank{2.7cm} & \blank{2.7cm} & \blank{1.3cm} & \blank{2.05cm} \\
|
||||
8 & verifier & \blank{2.7cm} & \blank{2.7cm} & \blank{1.3cm} & \blank{2.05cm} \\
|
||||
\bottomrule
|
||||
\end{tabularx}
|
||||
\renewcommand{\arraystretch}{1}
|
||||
|
||||
\section*{Trzy znaczniki jako dowód wywłaszczenia}
|
||||
|
||||
Kod A zapisuje \texttt{BEFORE=1}, podnosi B do priorytetu 3, a po powrocie z
|
||||
API zapisuje \texttt{AFTER=3}. Kod B zapisuje \texttt{HIGH=2} natychmiast po
|
||||
uzyskaniu CPU.
|
||||
|
||||
\begin{lstlisting}
|
||||
append_priority_order(BEFORE); // A: 1
|
||||
peer.set_priority(3); // B staje sie wyzej priorytetowe
|
||||
append_priority_order(AFTER); // A: 3, dopiero po powrocie
|
||||
|
||||
// B, zanim wywolanie w A zdazy wrocic:
|
||||
append_priority_order(HIGH); // B: 2
|
||||
\end{lstlisting}
|
||||
|
||||
Gdyby nie doszło do natychmiastowego wywłaszczenia, możliwa kolejność
|
||||
wynosiłaby \blank{4cm}. Odczyt oczekiwany: \blank{4cm}.
|
||||
|
||||
\section*{Osiem rekordów, ale żadnego użycia wiszącego uchwytu}
|
||||
|
||||
Po usunięciu zadania jego TCB może zostać odzyskany przez idle task.
|
||||
\texttt{TaskRef} nie posiada TCB i nie wydłuża jego życia. Dlatego terminalny
|
||||
rekord zapisuje znany stan \texttt{DELETED}, ale nie wywołuje
|
||||
\texttt{eTaskGetState()} przez stary uchwyt.
|
||||
|
||||
\newpage
|
||||
\section{Uruchomienie i kontrakt dowodu}
|
||||
|
||||
\begin{lstlisting}[language=bash]
|
||||
make check
|
||||
riscv64-unknown-elf-gdb build/task01_scheduler_states/prog.elf
|
||||
\end{lstlisting}
|
||||
|
||||
\begin{lstlisting}
|
||||
p g_alternating_tasks
|
||||
p g_alternating_ticks
|
||||
p g_snapshots
|
||||
p g_delay_start_tick
|
||||
p g_delay_observed_tick
|
||||
p g_delay_end_tick
|
||||
p g_delay_elapsed
|
||||
p g_priority_order
|
||||
p g_scheduler_states_pass
|
||||
\end{lstlisting}
|
||||
|
||||
\noindent\begin{tabularx}{\textwidth}{@{}p{5.2cm}X@{}}
|
||||
\toprule
|
||||
Warunek & Odczyt ucznia \\
|
||||
\midrule
|
||||
identyfikatory mają postać X,Y,X, $X\ne Y$ & \blank{6cm} \\
|
||||
w zdarzeniu 3: A=BLOCKED, B=RUNNING & \blank{6cm} \\
|
||||
\texttt{delay\_end - delay\_start == 3} & \blank{6cm} \\
|
||||
obserwacja blokady jest przed końcem delay & \blank{6cm} \\
|
||||
w zdarzeniu 6 B ma priorytet 3 & \blank{6cm} \\
|
||||
\texttt{priority\_order == \{1,2,3\}} & \blank{6cm} \\
|
||||
osiem snapshotów i \texttt{pass == 1} & \blank{6cm} \\
|
||||
\bottomrule
|
||||
\end{tabularx}
|
||||
|
||||
\section*{Minimalne wrappery C++}
|
||||
|
||||
\begin{lstlisting}
|
||||
class TaskRef final {
|
||||
public:
|
||||
explicit TaskRef(TaskHandle_t h) : handle_{h} {}
|
||||
eTaskState state() const { return eTaskGetState(handle_); }
|
||||
UBaseType_t priority() const { return uxTaskPriorityGet(handle_); }
|
||||
void set_priority(UBaseType_t p) const {
|
||||
vTaskPrioritySet(handle_, p);
|
||||
}
|
||||
private:
|
||||
TaskHandle_t handle_; // non-owning
|
||||
};
|
||||
\end{lstlisting}
|
||||
|
||||
Nie ma tu wirtualności, alokacji ani automatycznego delete. Rozmiar
|
||||
\texttt{TaskRef} jest równy rozmiarowi uchwytu. Pełna polityka własności taska
|
||||
pojawi się dopiero w K07--K09.
|
||||
|
||||
\section*{Wyjście — cztery krótkie odpowiedzi}
|
||||
|
||||
\begin{enumerate}
|
||||
\item Dlaczego zadanie o priorytecie 4 może nie działać, gdy działa p2?\\[1em]
|
||||
\item Dlaczego test nie wymaga, by A było pierwsze w śladzie time slicing?\\[1em]
|
||||
\item Kiedy \texttt{vTaskDelay(3)} oznacza dokładnie 3 ms?\\[1em]
|
||||
\item Co dokładnie dowodzi kolejność \texttt{1,2,3}?\\[1em]
|
||||
\end{enumerate}
|
||||
|
||||
\section*{Zaliczenie}
|
||||
|
||||
\begin{itemize}
|
||||
\item $\square$ rozróżniam READY, RUNNING, BLOCKED i DELETED;
|
||||
\item $\square$ pokazuję X--Y--X, blokadę na 3 ticki i porządek 1--2--3;
|
||||
\item $\square$ odróżniam delay względny od okresowego terminu;
|
||||
\item $\square$ nie utożsamiam ticka z milisekundą bez konfiguracji;
|
||||
\item $\square$ wiem, że \texttt{TaskRef} nie jest właścicielem TCB.
|
||||
\end{itemize}
|
||||
|
||||
\vfill
|
||||
\noindent\textbf{Następna karta K05:} most C++ do heapu, porównanie modeli
|
||||
FreeRTOS oraz tylko-odczytowy \texttt{HeapStats}.
|
||||
|
||||
\end{document}
|
||||
BIN
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Reference in New Issue
Block a user