mirror of
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f6ecf80ebb
The documentation grew one page at a time, so the tree follows the
history of who wrote what and not the shape of NuttX. Scheduling is
spread over three places, a driver page can sit above the subsystem
that owns it, and the front page lists everything at the same level.
That is a lot to face when all you want to know is where the scheduler
lives.
This change files every page under the code it describes. It is a move,
not a rewrite: outside the ten pages named below, every page keeps the
text that is already in master, and no page's text is deleted.
What it does:
* Groups the table of contents into nine chapters.
* Moves the OS subsystems under os/: scheduling, memory, drivers,
filesystem, networking, IPC, interrupts, libs, time.
* Renames the platform pages to the names the source tree uses, and
derives their tags from the tree instead of by hand.
* Splits guides/ by subject.
* Adds Documentation/redirects.py, with a rule for every page that left
its old path, so old URLs keep working. The redirect page also carries
a link's #anchor across to the new page.
Ten pages have text that is new or rewritten. Nine of them are the
landing page of a chapter, which has to exist for the new structure:
index the front page
os/index OS Design
os/scheduling/index Scheduling
os/interrupts/index Interrupts
os/ipc/index IPC
os/time/index Time and timers
about/index About
developing/index Developing NuttX
ReleaseNotes/index Release notes
The tenth is os/libs/libbuiltin, the only page here with technical
content: libs/libbuiltin/ had no page at all. Five SVG diagrams come
with these pages, hand-written XML with no editor metadata.
Nothing outside Documentation/ is touched.
How it was checked:
* Sphinx builds with -W: no warnings, and no document left outside a
toctree.
* A script, offered in the PR, proves the narrow claim this rests on.
For every page outside the ten named above it erases what a move
touches -- link target, path, tag line, toctree block, table border --
from the whole old text and the whole new text, and requires the two
to be byte for byte identical. It also requires every sentence of a
deleted page to turn up somewhere, and every page that left its old
path to have a redirect, from a URL that existed, to where its content
went. It exits non-zero and names the page if any of that is not true,
and it tests added pages too, so forgetting to declare one cannot make
it pass.
* An independent audit checked 133 factual claims on these ten pages
against the tree, one shell command per claim: 130 confirmed, 1
refuted and fixed here, 2 not checkable.
* tools/checkpatch.sh is clean over the range.
The diff is large because moving a page changes every link that points
to it. Most of it is pure renames, and board pages that gained one tag
line.
Assisted-by: Claude:claude-opus-5
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3.6 KiB
ReStructuredText
96 lines
3.6 KiB
ReStructuredText
====================
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Task Trace Internals
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====================
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Overview
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========
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.. image:: image/task-trace-internal.png
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The Task Trace is constructed by the following functions.
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NuttX kernel events collection
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------------------------------
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The kernel events are collected by ``sched_note_*()`` API calls embedded in NuttX kernel.
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- For task switch events
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- ``sched_note_start()``
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- ``sched_note_stop()``
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- ``sched_note_suspend()``
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- ``sched_note_resume()``
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- For system call events
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- ``sched_note_syscall_enter()``
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- ``sched_note_syscall_leave()``
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- For interrupt event
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- ``sched_note_irqhandler()``
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Filter logic (``nuttx/sched/sched_note.c``)
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-------------------------------------------
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- The ``sched_note_*()`` APIs are implemented here.
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- Filter the notes and pass them to noteram driver by ``sched_note_add()`` API.
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Noteram device driver (``nuttx/drivers/note/noteram_driver.c``)
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---------------------------------------------------------------
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- Accumurate incoming note records into the buffer.
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- Read the note records from the buffer by user requests.
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- The notes are recorded in the binary format of ``struct note_*_s``.
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- The detail function is described in :doc:`../os/drivers/character/note`.
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Notectl device driver (``nuttx/drivers/note/notectl_driver.c``)
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---------------------------------------------------------------
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- ``/dev/notectl`` device driver.
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- Control the filter logic in ``sched_note.c`` by calling note filter APIs.
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- The detail function is described in :doc:`../os/drivers/character/note`.
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"``trace``" Built-In Application (``apps/system/trace/trace.c``)
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----------------------------------------------------------------
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- ``trace`` Built-In Application to control the trace function interactively.
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- Read binary note records from ``/dev/note`` and convert into the ftrace text format which is acceptable by `"Trace Compass" <https://www.eclipse.org/tracecompass/>`_.
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- The command syntax is described in :doc:`tasktraceuser`.
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Getting the system call events
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==============================
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To get the system call events, two different methods are used for FLAT build and PROTECTED/KERNEL build.
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FLAT build
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----------
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In FLAT build, a system call is just a function call into the NuttX kernel.
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.. image:: image/syscall-flat-before.png
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To get the system call events, `wrapper function option <https://sourceware.org/binutils/docs/ld/Options.html#index-_002d_002dwrap_003dsymbol>`_ of the GNU Linker is used.
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The mksyscall tool is fixed to generate the system call wrapper which call system call enter/leave hook.
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The wrapper supersedes the system call function call of the NuttX binary by passing ``--wrap`` linker option to the build system.
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The wrapper calls the system call hooks before and after calling the real system call function.
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.. image:: image/syscall-flat-after.png
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PROTECTED/KERNEL build
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----------------------
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Different to FLAT build, in PROTECTED and KERNEL build, a system call is issued by an user space is handled as the following steps.
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#. System call issued by an application code is handled by the system call proxy (automatically generated by mksyscall).
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#. System call proxy issues the supervisor call instruction to enter into the kernel space.
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#. System call handler in the kernel space calls the system call stub (automatically generated by mksyscall).
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#. System call stub calls the API implementation in the NuttX kernel.
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.. image:: image/syscall-protected-before.png
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To get the system call events, the mksyscall tool is fixed to generate the system call wrapper which supersedes the system call function call in the system call stub.
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.. image:: image/syscall-protected-after.png
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