mirror of
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2025-09-04 20:19:47 +08:00
03abeaa63c
Add man page and kernel documentation for the sched monitors, as sched is a container of other monitors, document all in the same page. sched is the first nested monitor, also explain what is a nested monitor and how enabling containers or children monitors work. To: Ingo Molnar <mingo@redhat.com> To: Peter Zijlstra <peterz@infradead.org> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Jonathan Corbet <corbet@lwn.net> Cc: John Kacur <jkacur@redhat.com> Cc: Clark Williams <williams@redhat.com> Link: https://lore.kernel.org/20250305140406.350227-9-gmonaco@redhat.com Signed-off-by: Gabriele Monaco <gmonaco@redhat.com> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
172 lines
6.0 KiB
ReStructuredText
172 lines
6.0 KiB
ReStructuredText
Scheduler monitors
|
|
==================
|
|
|
|
- Name: sched
|
|
- Type: container for multiple monitors
|
|
- Author: Gabriele Monaco <gmonaco@redhat.com>, Daniel Bristot de Oliveira <bristot@kernel.org>
|
|
|
|
Description
|
|
-----------
|
|
|
|
Monitors describing complex systems, such as the scheduler, can easily grow to
|
|
the point where they are just hard to understand because of the many possible
|
|
state transitions.
|
|
Often it is possible to break such descriptions into smaller monitors,
|
|
sharing some or all events. Enabling those smaller monitors concurrently is,
|
|
in fact, testing the system as if we had one single larger monitor.
|
|
Splitting models into multiple specification is not only easier to
|
|
understand, but gives some more clues when we see errors.
|
|
|
|
The sched monitor is a set of specifications to describe the scheduler behaviour.
|
|
It includes several per-cpu and per-task monitors that work independently to verify
|
|
different specifications the scheduler should follow.
|
|
|
|
To make this system as straightforward as possible, sched specifications are *nested*
|
|
monitors, whereas sched itself is a *container*.
|
|
From the interface perspective, sched includes other monitors as sub-directories,
|
|
enabling/disabling or setting reactors to sched, propagates the change to all monitors,
|
|
however single monitors can be used independently as well.
|
|
|
|
It is important that future modules are built after their container (sched, in
|
|
this case), otherwise the linker would not respect the order and the nesting
|
|
wouldn't work as expected.
|
|
To do so, simply add them after sched in the Makefile.
|
|
|
|
Specifications
|
|
--------------
|
|
|
|
The specifications included in sched are currently a work in progress, adapting the ones
|
|
defined in by Daniel Bristot in [1].
|
|
|
|
Currently we included the following:
|
|
|
|
Monitor tss
|
|
~~~~~~~~~~~
|
|
|
|
The task switch while scheduling (tss) monitor ensures a task switch happens
|
|
only in scheduling context, that is inside a call to `__schedule`::
|
|
|
|
|
|
|
|
|
|
v
|
|
+-----------------+
|
|
| thread | <+
|
|
+-----------------+ |
|
|
| |
|
|
| schedule_entry | schedule_exit
|
|
v |
|
|
sched_switch |
|
|
+--------------- |
|
|
| sched |
|
|
+--------------> -+
|
|
|
|
Monitor sco
|
|
~~~~~~~~~~~
|
|
|
|
The scheduling context operations (sco) monitor ensures changes in a task state
|
|
happen only in thread context::
|
|
|
|
|
|
|
|
|
|
|
|
v
|
|
sched_set_state +------------------+
|
|
+------------------ | |
|
|
| | thread_context |
|
|
+-----------------> | | <+
|
|
+------------------+ |
|
|
| |
|
|
| schedule_entry | schedule_exit
|
|
v |
|
|
|
|
|
scheduling_context -+
|
|
|
|
Monitor snroc
|
|
~~~~~~~~~~~~~
|
|
|
|
The set non runnable on its own context (snroc) monitor ensures changes in a
|
|
task state happens only in the respective task's context. This is a per-task
|
|
monitor::
|
|
|
|
|
|
|
|
|
|
v
|
|
+------------------+
|
|
| other_context | <+
|
|
+------------------+ |
|
|
| |
|
|
| sched_switch_in | sched_switch_out
|
|
v |
|
|
sched_set_state |
|
|
+------------------ |
|
|
| own_context |
|
|
+-----------------> -+
|
|
|
|
Monitor scpd
|
|
~~~~~~~~~~~~
|
|
|
|
The schedule called with preemption disabled (scpd) monitor ensures schedule is
|
|
called with preemption disabled::
|
|
|
|
|
|
|
|
|
|
v
|
|
+------------------+
|
|
| cant_sched | <+
|
|
+------------------+ |
|
|
| |
|
|
| preempt_disable | preempt_enable
|
|
v |
|
|
schedule_entry |
|
|
schedule_exit |
|
|
+----------------- can_sched |
|
|
| |
|
|
+----------------> -+
|
|
|
|
Monitor snep
|
|
~~~~~~~~~~~~
|
|
|
|
The schedule does not enable preempt (snep) monitor ensures a schedule call
|
|
does not enable preemption::
|
|
|
|
|
|
|
|
|
|
v
|
|
preempt_disable +------------------------+
|
|
preempt_enable | |
|
|
+------------------ | non_scheduling_context |
|
|
| | |
|
|
+-----------------> | | <+
|
|
+------------------------+ |
|
|
| |
|
|
| schedule_entry | schedule_exit
|
|
v |
|
|
|
|
|
scheduling_contex -+
|
|
|
|
Monitor sncid
|
|
~~~~~~~~~~~~~
|
|
|
|
The schedule not called with interrupt disabled (sncid) monitor ensures
|
|
schedule is not called with interrupt disabled::
|
|
|
|
|
|
|
|
|
|
v
|
|
schedule_entry +--------------+
|
|
schedule_exit | |
|
|
+----------------- | can_sched |
|
|
| | |
|
|
+----------------> | | <+
|
|
+--------------+ |
|
|
| |
|
|
| irq_disable | irq_enable
|
|
v |
|
|
|
|
|
cant_sched -+
|
|
|
|
References
|
|
----------
|
|
|
|
[1] - https://bristot.me/linux-task-model
|