€•8æ      Œsphinx.addnodes”Œdocument”“”)”}”(Œ	rawsource”Œ ”Œchildren”]”(Œtranslations”ŒLanguagesNode”“”)”}”(hhh]”(h Œpending_xref”“”)”}”(hhh]”Œdocutils.nodes”ŒText”“”ŒChinese (Simplified)”…””}”Œparent”hsbaŒ
attributes”}”(Œids”]”Œclasses”]”Œnames”]”Œdupnames”]”Œbackrefs”]”Œ	refdomain”Œstd”Œreftype”Œdoc”Œ	reftarget”Œ*/translations/zh_CN/trace/rv/monitor_sched”Œmodname”NŒ	classname”NŒrefexplicit”ˆuŒtagname”hhhubh)”}”(hhh]”hŒChinese (Traditional)”…””}”hh2sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ*/translations/zh_TW/trace/rv/monitor_sched”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ*/translations/it_IT/trace/rv/monitor_sched”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ*/translations/ja_JP/trace/rv/monitor_sched”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ*/translations/ko_KR/trace/rv/monitor_sched”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ*/translations/sp_SP/trace/rv/monitor_sched”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒScheduler monitors”h]”hŒScheduler monitors”…””}”(hh¨hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hh£hžhhŸŒD/var/lib/git/docbuild/linux/Documentation/trace/rv/monitor_sched.rst”h KubhŒbullet_list”“”)”}”(hhh]”(hŒ	list_item”“”)”}”(hŒName: sched”h]”hŒ	paragraph”“”)”}”(hhÀh]”hŒName: sched”…””}”(hhÄhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h Khh¾ubah}”(h]”h ]”h"]”h$]”h&]”uh1h¼hh¹hžhhŸh¶h Nubh½)”}”(hŒ%Type: container for multiple monitors”h]”hÃ)”}”(hhÙh]”hŒ%Type: container for multiple monitors”…””}”(hhÛhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h Khh×ubah}”(h]”h ]”h"]”h$]”h&]”uh1h¼hh¹hžhhŸh¶h Nubh½)”}”(hŒ^Author: Gabriele Monaco <gmonaco@redhat.com>, Daniel Bristot de Oliveira <bristot@kernel.org>
”h]”hÃ)”}”(hŒ]Author: Gabriele Monaco <gmonaco@redhat.com>, Daniel Bristot de Oliveira <bristot@kernel.org>”h]”(hŒAuthor: Gabriele Monaco <”…””}”(hhòhžhhŸNh NubhŒ	reference”“”)”}”(hŒgmonaco@redhat.com”h]”hŒgmonaco@redhat.com”…””}”(hhühžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”Œmailto:gmonaco@redhat.com”uh1húhhòubhŒ>, Daniel Bristot de Oliveira <”…””}”(hhòhžhhŸNh Nubhû)”}”(hŒbristot@kernel.org”h]”hŒbristot@kernel.org”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”Œmailto:bristot@kernel.org”uh1húhhòubhŒ>”…””}”(hhòhžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h Khhîubah}”(h]”h ]”h"]”h$]”h&]”uh1h¼hh¹hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ-”uh1h·hŸh¶h Khh£hžhubh¢)”}”(hhh]”(h§)”}”(hŒDescription”h]”hŒDescription”…””}”(hj;  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj8  hžhhŸh¶h K	ubhÃ)”}”(hX  Monitors describing complex systems, such as the scheduler, can easily grow to
the point where they are just hard to understand because of the many possible
state transitions.
Often it is possible to break such descriptions into smaller monitors,
sharing some or all events. Enabling those smaller monitors concurrently is,
in fact, testing the system as if we had one single larger monitor.
Splitting models into multiple specification is not only easier to
understand, but gives some more clues when we see errors.”h]”hX  Monitors describing complex systems, such as the scheduler, can easily grow to
the point where they are just hard to understand because of the many possible
state transitions.
Often it is possible to break such descriptions into smaller monitors,
sharing some or all events. Enabling those smaller monitors concurrently is,
in fact, testing the system as if we had one single larger monitor.
Splitting models into multiple specification is not only easier to
understand, but gives some more clues when we see errors.”…””}”(hjI  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h Khj8  hžhubhÃ)”}”(hŒÛThe 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.”h]”hŒÛThe 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.”…””}”(hjW  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h Khj8  hžhubhÃ)”}”(hXk  To make this system as straightforward as possible, sched specifications are *nested*
monitors, whereas sched itself is a *container*.
From the interface perspective, sched includes other monitors as sub-directories,
enabling/disabling or setting reactors to sched, propagates the change to all monitors,
however single monitors can be used independently as well.”h]”(hŒMTo make this system as straightforward as possible, sched specifications are ”…””}”(hje  hžhhŸNh NubhŒemphasis”“”)”}”(hŒ*nested*”h]”hŒnested”…””}”(hjo  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jm  hje  ubhŒ%
monitors, whereas sched itself is a ”…””}”(hje  hžhhŸNh Nubjn  )”}”(hŒ*container*”h]”hŒ	container”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jm  hje  ubhŒæ.
From the interface perspective, sched includes other monitors as sub-directories,
enabling/disabling or setting reactors to sched, propagates the change to all monitors,
however single monitors can be used independently as well.”…””}”(hje  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h Khj8  hžhubhÃ)”}”(hŒíIt 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.”h]”hŒïIt 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
wouldnâ€™t work as expected.
To do so, simply add them after sched in the Makefile.”…””}”(hj™  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h Khj8  hžhubeh}”(h]”Œdescription”ah ]”h"]”Œdescription”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K	ubh¢)”}”(hhh]”(h§)”}”(hŒSpecifications”h]”hŒSpecifications”…””}”(hj²  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj¯  hžhhŸh¶h K$ubhÃ)”}”(hŒ}The specifications included in sched are currently a work in progress, adapting the ones
defined in by Daniel Bristot in [1].”h]”hŒ}The specifications included in sched are currently a work in progress, adapting the ones
defined in by Daniel Bristot in [1].”…””}”(hjÀ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h K&hj¯  hžhubhÃ)”}”(hŒ$Currently we included the following:”h]”hŒ$Currently we included the following:”…””}”(hjÎ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h K)hj¯  hžhubh¢)”}”(hhh]”(h§)”}”(hŒMonitor sco”h]”hŒMonitor sco”…””}”(hjß  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjÜ  hžhhŸh¶h K,ubhÃ)”}”(hŒoThe scheduling context operations (sco) monitor ensures changes in a task state
happen only in thread context::”h]”hŒnThe scheduling context operations (sco) monitor ensures changes in a task state
happen only in thread context:”…””}”(hjí  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h K.hjÜ  hžhubhŒliteral_block”“”)”}”(hX                        |
                      |
                      v
  sched_set_state   +------------------+
+------------------ |                  |
|                   |  thread_context  |
+-----------------> |                  | <+
                    +------------------+  |
                      |                   |
                      | schedule_entry    | schedule_exit
                      v                   |
                                          |
                     scheduling_context  -+”h]”hX                        |
                      |
                      v
  sched_set_state   +------------------+
+------------------ |                  |
|                   |  thread_context  |
+-----------------> |                  | <+
                    +------------------+  |
                      |                   |
                      | schedule_entry    | schedule_exit
                      v                   |
                                          |
                     scheduling_context  -+”…””}”hjý  sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1jû  hŸh¶h K2hjÜ  hžhubeh}”(h]”Œmonitor-sco”ah ]”h"]”Œmonitor sco”ah$]”h&]”uh1h¡hj¯  hžhhŸh¶h K,ubh¢)”}”(hhh]”(h§)”}”(hŒMonitor snroc”h]”hŒMonitor snroc”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj  hžhhŸh¶h KAubhÃ)”}”(hŒ£The set non runnable on its own context (snroc) monitor ensures changes in a
task state happens only in the respective task's context. This is a per-task
monitor::”h]”hŒ¤The set non runnable on its own context (snroc) monitor ensures changes in a
task state happens only in the respective taskâ€™s context. This is a per-task
monitor:”…””}”(hj&  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h KChj  hžhubjü  )”}”(hX                        |
                      |
                      v
                    +------------------+
                    |  other_context   | <+
                    +------------------+  |
                      |                   |
                      | sched_switch_in   | sched_switch_out
                      v                   |
  sched_set_state                         |
+------------------                       |
|                       own_context       |
+----------------->                      -+”h]”hX                        |
                      |
                      v
                    +------------------+
                    |  other_context   | <+
                    +------------------+  |
                      |                   |
                      | sched_switch_in   | sched_switch_out
                      v                   |
  sched_set_state                         |
+------------------                       |
|                       own_context       |
+----------------->                      -+”…””}”hj4  sbah}”(h]”h ]”h"]”h$]”h&]”j  j  uh1jû  hŸh¶h KGhj  hžhubeh}”(h]”Œmonitor-snroc”ah ]”h"]”Œmonitor snroc”ah$]”h&]”uh1h¡hj¯  hžhhŸh¶h KAubh¢)”}”(hhh]”(h§)”}”(hŒMonitor scpd”h]”hŒMonitor scpd”…””}”(hjM  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjJ  hžhhŸh¶h KVubhÃ)”}”(hŒqThe schedule called with preemption disabled (scpd) monitor ensures schedule is
called with preemption disabled::”h]”hŒpThe schedule called with preemption disabled (scpd) monitor ensures schedule is
called with preemption disabled:”…””}”(hj[  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h KXhjJ  hžhubjü  )”}”(hX)                       |
                     |
                     v
                   +------------------+
                   |    cant_sched    | <+
                   +------------------+  |
                     |                   |
                     | preempt_disable   | preempt_enable
                     v                   |
  schedule_entry                         |
  schedule_exit                          |
+-----------------      can_sched        |
|                                        |
+---------------->                      -+”h]”hX)                       |
                     |
                     v
                   +------------------+
                   |    cant_sched    | <+
                   +------------------+  |
                     |                   |
                     | preempt_disable   | preempt_enable
                     v                   |
  schedule_entry                         |
  schedule_exit                          |
+-----------------      can_sched        |
|                                        |
+---------------->                      -+”…””}”hji  sbah}”(h]”h ]”h"]”h$]”h&]”j  j  uh1jû  hŸh¶h K[hjJ  hžhubeh}”(h]”Œmonitor-scpd”ah ]”h"]”Œmonitor scpd”ah$]”h&]”uh1h¡hj¯  hžhhŸh¶h KVubh¢)”}”(hhh]”(h§)”}”(hŒMonitor snep”h]”hŒMonitor snep”…””}”(hj‚  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj  hžhhŸh¶h KkubhÃ)”}”(hŒhThe schedule does not enable preempt (snep) monitor ensures a schedule call
does not enable preemption::”h]”hŒgThe schedule does not enable preempt (snep) monitor ensures a schedule call
does not enable preemption:”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h Kmhj  hžhubjü  )”}”(hXo                        |
                      |
                      v
  preempt_disable   +------------------------+
  preempt_enable    |                        |
+------------------ | non_scheduling_context |
|                   |                        |
+-----------------> |                        | <+
                    +------------------------+  |
                      |                         |
                      | schedule_entry          | schedule_exit
                      v                         |
                                                |
                        scheduling_contex      -+”h]”hXo                        |
                      |
                      v
  preempt_disable   +------------------------+
  preempt_enable    |                        |
+------------------ | non_scheduling_context |
|                   |                        |
+-----------------> |                        | <+
                    +------------------------+  |
                      |                         |
                      | schedule_entry          | schedule_exit
                      v                         |
                                                |
                        scheduling_contex      -+”…””}”hjž  sbah}”(h]”h ]”h"]”h$]”h&]”j  j  uh1jû  hŸh¶h Kphj  hžhubeh}”(h]”Œmonitor-snep”ah ]”h"]”Œmonitor snep”ah$]”h&]”uh1h¡hj¯  hžhhŸh¶h Kkubh¢)”}”(hhh]”(h§)”}”(hŒMonitor sts”h]”hŒMonitor sts”…””}”(hj·  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj´  hžhhŸh¶h K€ubhÃ)”}”(hX‚  The schedule implies task switch (sts) monitor ensures a task switch happens
only in scheduling context and up to once, as well as scheduling occurs with
interrupts enabled but no task switch can happen before interrupts are
disabled. When the next task picked for execution is the same as the previously
running one, no real task switch occurs but interrupts are disabled nonetheless::”h]”hX  The schedule implies task switch (sts) monitor ensures a task switch happens
only in scheduling context and up to once, as well as scheduling occurs with
interrupts enabled but no task switch can happen before interrupts are
disabled. When the next task picked for execution is the same as the previously
running one, no real task switch occurs but interrupts are disabled nonetheless:”…””}”(hjÅ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h K‚hj´  hžhubjü  )”}”(hXÞ     irq_entry                      |
    +----+                        |
    v    |                        v
+------------+ irq_enable    #===================#   irq_disable
|            | ------------> H                   H   irq_entry
| cant_sched | <------------ H                   H   irq_enable
|            | irq_disable   H     can_sched     H --------------+
+------------+               H                   H               |
                             H                   H               |
           +---------------> H                   H <-------------+
           |                 #===================#
           |                   |
     schedule_exit             | schedule_entry
           |                   v
           |   +-------------------+     irq_enable
           |   |    scheduling     | <---------------+
           |   +-------------------+                 |
           |     |                                   |
           |     | irq_disable                    +--------+  irq_entry
           |     v                                |        | --------+
           |   +-------------------+  irq_entry   | in_irq |         |
           |   |                   | -----------> |        | <-------+
           |   | disable_to_switch |              +--------+
           |   |                   | --+
           |   +-------------------+   |
           |     |                     |
           |     | sched_switch        |
           |     v                     |
           |   +-------------------+   |
           |   |     switching     |   | irq_enable
           |   +-------------------+   |
           |     |                     |
           |     | irq_enable          |
           |     v                     |
           |   +-------------------+   |
           +-- |  enable_to_exit   | <-+
               +-------------------+
                 ^               | irq_disable
                 |               | irq_entry
                 +---------------+ irq_enable”h]”hXÞ     irq_entry                      |
    +----+                        |
    v    |                        v
+------------+ irq_enable    #===================#   irq_disable
|            | ------------> H                   H   irq_entry
| cant_sched | <------------ H                   H   irq_enable
|            | irq_disable   H     can_sched     H --------------+
+------------+               H                   H               |
                             H                   H               |
           +---------------> H                   H <-------------+
           |                 #===================#
           |                   |
     schedule_exit             | schedule_entry
           |                   v
           |   +-------------------+     irq_enable
           |   |    scheduling     | <---------------+
           |   +-------------------+                 |
           |     |                                   |
           |     | irq_disable                    +--------+  irq_entry
           |     v                                |        | --------+
           |   +-------------------+  irq_entry   | in_irq |         |
           |   |                   | -----------> |        | <-------+
           |   | disable_to_switch |              +--------+
           |   |                   | --+
           |   +-------------------+   |
           |     |                     |
           |     | sched_switch        |
           |     v                     |
           |   +-------------------+   |
           |   |     switching     |   | irq_enable
           |   +-------------------+   |
           |     |                     |
           |     | irq_enable          |
           |     v                     |
           |   +-------------------+   |
           +-- |  enable_to_exit   | <-+
               +-------------------+
                 ^               | irq_disable
                 |               | irq_entry
                 +---------------+ irq_enable”…””}”hjÓ  sbah}”(h]”h ]”h"]”h$]”h&]”j  j  uh1jû  hŸh¶h Kˆhj´  hžhubeh}”(h]”Œmonitor-sts”ah ]”h"]”Œmonitor sts”ah$]”h&]”uh1h¡hj¯  hžhhŸh¶h K€ubeh}”(h]”Œspecifications”ah ]”h"]”Œspecifications”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K$ubh¢)”}”(hhh]”(h§)”}”(hŒMonitor nrp”h]”hŒMonitor nrp”…””}”(hjô  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjñ  hžhhŸh¶h K²ubhÃ)”}”(hXÕ  The need resched preempts (nrp) monitor ensures preemption requires
``need_resched``. Only kernel preemption is considered, since preemption
while returning to userspace, for this monitor, is indistinguishable from
``sched_switch_yield`` (described in the sssw monitor).
A kernel preemption is whenever ``__schedule`` is called with the preemption
flag set to true (e.g. from preempt_enable or exiting from interrupts). This
type of preemption occurs after the need for ``rescheduling`` has been set.
This is not valid for the *lazy* variant of the flag, which causes only
userspace preemption.
A ``schedule_entry_preempt`` may involve a task switch or not, in the latter
case, a task goes through the scheduler from a preemption context but it is
picked as the next task to run. Since the scheduler runs, this clears the need
to reschedule. The ``any_thread_running`` state does not imply the monitored
task is not running as this monitor does not track the outcome of scheduling.”h]”(hŒDThe need resched preempts (nrp) monitor ensures preemption requires
”…””}”(hj  hžhhŸNh NubhŒliteral”“”)”}”(hŒ``need_resched``”h]”hŒneed_resched”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj  ubhŒƒ. Only kernel preemption is considered, since preemption
while returning to userspace, for this monitor, is indistinguishable from
”…””}”(hj  hžhhŸNh Nubj  )”}”(hŒ``sched_switch_yield``”h]”hŒsched_switch_yield”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj  ubhŒB (described in the sssw monitor).
A kernel preemption is whenever ”…””}”(hj  hžhhŸNh Nubj  )”}”(hŒ``__schedule``”h]”hŒ
__schedule”…””}”(hj0  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj  ubhŒ™ is called with the preemption
flag set to true (e.g. from preempt_enable or exiting from interrupts). This
type of preemption occurs after the need for ”…””}”(hj  hžhhŸNh Nubj  )”}”(hŒ``rescheduling``”h]”hŒrescheduling”…””}”(hjB  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj  ubhŒ) has been set.
This is not valid for the ”…””}”(hj  hžhhŸNh Nubjn  )”}”(hŒ*lazy*”h]”hŒlazy”…””}”(hjT  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jm  hj  ubhŒ@ variant of the flag, which causes only
userspace preemption.
A ”…””}”(hj  hžhhŸNh Nubj  )”}”(hŒ``schedule_entry_preempt``”h]”hŒschedule_entry_preempt”…””}”(hjf  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj  ubhŒß may involve a task switch or not, in the latter
case, a task goes through the scheduler from a preemption context but it is
picked as the next task to run. Since the scheduler runs, this clears the need
to reschedule. The ”…””}”(hj  hžhhŸNh Nubj  )”}”(hŒ``any_thread_running``”h]”hŒany_thread_running”…””}”(hjx  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj  ubhŒq state does not imply the monitored
task is not running as this monitor does not track the outcome of scheduling.”…””}”(hj  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h K´hjñ  hžhubhÃ)”}”(hŒÎIn theory, a preemption can only occur after the ``need_resched`` flag is set. In
practice, however, it is possible to see a preemption where the flag is not
set. This can happen in one specific condition::”h]”(hŒ1In theory, a preemption can only occur after the ”…””}”(hj  hžhhŸNh Nubj  )”}”(hŒ``need_resched``”h]”hŒneed_resched”…””}”(hj˜  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj  ubhŒŒ flag is set. In
practice, however, it is possible to see a preemption where the flag is not
set. This can happen in one specific condition:”…””}”(hj  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h KÃhjñ  hžhubjü  )”}”(hŒâneed_resched
                 preempt_schedule()
                                         preempt_schedule_irq()
                                                 __schedule()
!need_resched
                         __schedule()”h]”hŒâneed_resched
                 preempt_schedule()
                                         preempt_schedule_irq()
                                                 __schedule()
!need_resched
                         __schedule()”…””}”hj°  sbah}”(h]”h ]”h"]”h$]”h&]”j  j  uh1jû  hŸh¶h KÇhjñ  hžhubhÃ)”}”(hXþ  In the situation above, standard preemption starts (e.g. from preempt_enable
when the flag is set), an interrupt occurs before scheduling and, on its exit
path, it schedules, which clears the ``need_resched`` flag.
When the preempted task runs again, the standard preemption started earlier
resumes, although the flag is no longer set. The monitor considers this a
``nested_preemption``, this allows another preemption without re-setting the
flag. This condition relaxes the monitor constraints and may catch false
negatives (i.e. no real ``nested_preemptions``) but makes the monitor more
robust and able to validate other scenarios.
For simplicity, the monitor starts in ``preempt_irq``, although no interrupt
occurred, as the situation above is hard to pinpoint::”h]”(hŒÀIn the situation above, standard preemption starts (e.g. from preempt_enable
when the flag is set), an interrupt occurs before scheduling and, on its exit
path, it schedules, which clears the ”…””}”(hj¾  hžhhŸNh Nubj  )”}”(hŒ``need_resched``”h]”hŒneed_resched”…””}”(hjÆ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj¾  ubhŒ flag.
When the preempted task runs again, the standard preemption started earlier
resumes, although the flag is no longer set. The monitor considers this a
”…””}”(hj¾  hžhhŸNh Nubj  )”}”(hŒ``nested_preemption``”h]”hŒnested_preemption”…””}”(hjØ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj¾  ubhŒ™, this allows another preemption without re-setting the
flag. This condition relaxes the monitor constraints and may catch false
negatives (i.e. no real ”…””}”(hj¾  hžhhŸNh Nubj  )”}”(hŒ``nested_preemptions``”h]”hŒnested_preemptions”…””}”(hjê  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj¾  ubhŒp) but makes the monitor more
robust and able to validate other scenarios.
For simplicity, the monitor starts in ”…””}”(hj¾  hžhhŸNh Nubj  )”}”(hŒ``preempt_irq``”h]”hŒpreempt_irq”…””}”(hjü  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj¾  ubhŒM, although no interrupt
occurred, as the situation above is hard to pinpoint:”…””}”(hj¾  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h KÎhjñ  hžhubjü  )”}”(hXö    schedule_entry
  irq_entry                 #===========================================#
+-------------------------- H                                           H
|                           H                                           H
+-------------------------> H             any_thread_running            H
                            H                                           H
+-------------------------> H                                           H
|                           #===========================================#
| schedule_entry              |                       ^
| schedule_entry_preempt      | sched_need_resched    | schedule_entry
|                             |                      schedule_entry_preempt
|                             v                       |
|                           +----------------------+  |
|                      +--- |                      |  |
|   sched_need_resched |    |     rescheduling     | -+
|                      +--> |                      |
|                           +----------------------+
|                             | irq_entry
|                             v
|                           +----------------------+
|                           |                      | ---+
|                      ---> |                      |    | sched_need_resched
|                           |      preempt_irq     |    | irq_entry
|                           |                      | <--+
|                           |                      | <--+
|                           +----------------------+    |
|                             | schedule_entry          | sched_need_resched
|                             | schedule_entry_preempt  |
|                             v                         |
|                           +-----------------------+   |
+-------------------------- |    nested_preempt     | --+
                            +-----------------------+
                              ^ irq_entry         |
                              +-------------------+”h]”hXö    schedule_entry
  irq_entry                 #===========================================#
+-------------------------- H                                           H
|                           H                                           H
+-------------------------> H             any_thread_running            H
                            H                                           H
+-------------------------> H                                           H
|                           #===========================================#
| schedule_entry              |                       ^
| schedule_entry_preempt      | sched_need_resched    | schedule_entry
|                             |                      schedule_entry_preempt
|                             v                       |
|                           +----------------------+  |
|                      +--- |                      |  |
|   sched_need_resched |    |     rescheduling     | -+
|                      +--> |                      |
|                           +----------------------+
|                             | irq_entry
|                             v
|                           +----------------------+
|                           |                      | ---+
|                      ---> |                      |    | sched_need_resched
|                           |      preempt_irq     |    | irq_entry
|                           |                      | <--+
|                           |                      | <--+
|                           +----------------------+    |
|                             | schedule_entry          | sched_need_resched
|                             | schedule_entry_preempt  |
|                             v                         |
|                           +-----------------------+   |
+-------------------------- |    nested_preempt     | --+
                            +-----------------------+
                              ^ irq_entry         |
                              +-------------------+”…””}”hj  sbah}”(h]”h ]”h"]”h$]”h&]”j  j  uh1jû  hŸh¶h KÚhjñ  hžhubhÃ)”}”(hX  Due to how the ``need_resched`` flag on the preemption count works on arm64,
this monitor is unstable on that architecture, as it often records preemption
when the flag is not set, even in presence of the workaround above.
For the time being, the monitor is disabled by default on arm64.”h]”(hŒDue to how the ”…””}”(hj"  hžhhŸNh Nubj  )”}”(hŒ``need_resched``”h]”hŒneed_resched”…””}”(hj*  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj"  ubhX    flag on the preemption count works on arm64,
this monitor is unstable on that architecture, as it often records preemption
when the flag is not set, even in presence of the workaround above.
For the time being, the monitor is disabled by default on arm64.”…””}”(hj"  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h Kýhjñ  hžhubeh}”(h]”Œmonitor-nrp”ah ]”h"]”Œmonitor nrp”ah$]”h&]”uh1h¡hh£hžhhŸh¶h K²ubh¢)”}”(hhh]”(h§)”}”(hŒMonitor sssw”h]”hŒMonitor sssw”…””}”(hjM  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjJ  hžhhŸh¶h MubhÃ)”}”(hŒ°The set state sleep and wakeup (sssw) monitor ensures ``set_state`` to
sleepable leads to sleeping and sleeping tasks require wakeup. It includes the
following types of switch:”h]”(hŒ6The set state sleep and wakeup (sssw) monitor ensures ”…””}”(hj[  hžhhŸNh Nubj  )”}”(hŒ``set_state``”h]”hŒ	set_state”…””}”(hjc  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj[  ubhŒm to
sleepable leads to sleeping and sleeping tasks require wakeup. It includes the
following types of switch:”…””}”(hj[  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h MhjJ  hžhubh¸)”}”(hhh]”(h½)”}”(hXT  ``switch_suspend``:
a task puts itself to sleep, this can happen only after explicitly setting
the task to ``sleepable``. After a task is suspended, it needs to be woken up
(``waking`` state) before being switched in again.
Setting the task's state to ``sleepable`` can be reverted before switching if it
is woken up or set to ``runnable``.”h]”hÃ)”}”(hXT  ``switch_suspend``:
a task puts itself to sleep, this can happen only after explicitly setting
the task to ``sleepable``. After a task is suspended, it needs to be woken up
(``waking`` state) before being switched in again.
Setting the task's state to ``sleepable`` can be reverted before switching if it
is woken up or set to ``runnable``.”h]”(j  )”}”(hŒ``switch_suspend``”h]”hŒswitch_suspend”…””}”(hj†  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj‚  ubhŒY:
a task puts itself to sleep, this can happen only after explicitly setting
the task to ”…””}”(hj‚  hžhhŸNh Nubj  )”}”(hŒ``sleepable``”h]”hŒ	sleepable”…””}”(hj˜  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj‚  ubhŒ6. After a task is suspended, it needs to be woken up
(”…””}”(hj‚  hžhhŸNh Nubj  )”}”(hŒ
``waking``”h]”hŒwaking”…””}”(hjª  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj‚  ubhŒF state) before being switched in again.
Setting the taskâ€™s state to ”…””}”(hj‚  hžhhŸNh Nubj  )”}”(hŒ``sleepable``”h]”hŒ	sleepable”…””}”(hj¼  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj‚  ubhŒ> can be reverted before switching if it
is woken up or set to ”…””}”(hj‚  hžhhŸNh Nubj  )”}”(hŒ``runnable``”h]”hŒrunnable”…””}”(hjÎ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj‚  ubhŒ.”…””}”(hj‚  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h M	hj~  ubah}”(h]”h ]”h"]”h$]”h&]”uh1h¼hj{  hžhhŸh¶h Nubh½)”}”(hXƒ  ``switch_blocking``:
a special case of a ``switch_suspend`` where the task is waiting on a
sleeping RT lock (``PREEMPT_RT`` only), it is common to see wakeup and set
state events racing with each other and this leads the model to perceive this
type of switch when the task is not set to sleepable. This is a limitation of
the model in SMP system and workarounds may slow down the system.”h]”hÃ)”}”(hXƒ  ``switch_blocking``:
a special case of a ``switch_suspend`` where the task is waiting on a
sleeping RT lock (``PREEMPT_RT`` only), it is common to see wakeup and set
state events racing with each other and this leads the model to perceive this
type of switch when the task is not set to sleepable. This is a limitation of
the model in SMP system and workarounds may slow down the system.”h]”(j  )”}”(hŒ``switch_blocking``”h]”hŒswitch_blocking”…””}”(hjô  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hjð  ubhŒ:
a special case of a ”…””}”(hjð  hžhhŸNh Nubj  )”}”(hŒ``switch_suspend``”h]”hŒswitch_suspend”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hjð  ubhŒ2 where the task is waiting on a
sleeping RT lock (”…””}”(hjð  hžhhŸNh Nubj  )”}”(hŒ``PREEMPT_RT``”h]”hŒ
PREEMPT_RT”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hjð  ubhX   only), it is common to see wakeup and set
state events racing with each other and this leads the model to perceive this
type of switch when the task is not set to sleepable. This is a limitation of
the model in SMP system and workarounds may slow down the system.”…””}”(hjð  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h Mhjì  ubah}”(h]”h ]”h"]”h$]”h&]”uh1h¼hj{  hžhhŸh¶h Nubh½)”}”(hŒq``switch_preempt``:
a task switch as a result of kernel preemption (``schedule_entry_preempt`` in
the nrp model).”h]”hÃ)”}”(hŒq``switch_preempt``:
a task switch as a result of kernel preemption (``schedule_entry_preempt`` in
the nrp model).”h]”(j  )”}”(hŒ``switch_preempt``”h]”hŒswitch_preempt”…””}”(hj>  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj:  ubhŒ2:
a task switch as a result of kernel preemption (”…””}”(hj:  hžhhŸNh Nubj  )”}”(hŒ``schedule_entry_preempt``”h]”hŒschedule_entry_preempt”…””}”(hjP  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj:  ubhŒ in
the nrp model).”…””}”(hj:  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h Mhj6  ubah}”(h]”h ]”h"]”h$]”h&]”uh1h¼hj{  hžhhŸh¶h Nubh½)”}”(hXê  ``switch_yield``:
a task explicitly calls the scheduler or is preempted while returning to
userspace. It can happen after a ``yield`` system call, from the idle task or
if the ``need_resched`` flag is set. By definition, a task cannot yield while
``sleepable`` as that would be a suspension. A special case of a yield occurs
when a task in ``TASK_INTERRUPTIBLE`` calls the scheduler while a signal is
pending. The task doesn't go through the usual blocking/waking and is set
back to runnable, the resulting switch (if there) looks like a yield to the
``signal_wakeup`` state and is followed by the signal delivery. From this
state, the monitor expects a signal even if it sees a wakeup event, although
not necessary, to rule out false negatives.
”h]”hÃ)”}”(hXé  ``switch_yield``:
a task explicitly calls the scheduler or is preempted while returning to
userspace. It can happen after a ``yield`` system call, from the idle task or
if the ``need_resched`` flag is set. By definition, a task cannot yield while
``sleepable`` as that would be a suspension. A special case of a yield occurs
when a task in ``TASK_INTERRUPTIBLE`` calls the scheduler while a signal is
pending. The task doesn't go through the usual blocking/waking and is set
back to runnable, the resulting switch (if there) looks like a yield to the
``signal_wakeup`` state and is followed by the signal delivery. From this
state, the monitor expects a signal even if it sees a wakeup event, although
not necessary, to rule out false negatives.”h]”(j  )”}”(hŒ``switch_yield``”h]”hŒswitch_yield”…””}”(hjv  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hjr  ubhŒl:
a task explicitly calls the scheduler or is preempted while returning to
userspace. It can happen after a ”…””}”(hjr  hžhhŸNh Nubj  )”}”(hŒ	``yield``”h]”hŒyield”…””}”(hjˆ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hjr  ubhŒ+ system call, from the idle task or
if the ”…””}”(hjr  hžhhŸNh Nubj  )”}”(hŒ``need_resched``”h]”hŒneed_resched”…””}”(hjš  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hjr  ubhŒ7 flag is set. By definition, a task cannot yield while
”…””}”(hjr  hžhhŸNh Nubj  )”}”(hŒ``sleepable``”h]”hŒ	sleepable”…””}”(hj¬  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hjr  ubhŒP as that would be a suspension. A special case of a yield occurs
when a task in ”…””}”(hjr  hžhhŸNh Nubj  )”}”(hŒ``TASK_INTERRUPTIBLE``”h]”hŒTASK_INTERRUPTIBLE”…””}”(hj¾  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hjr  ubhŒ¿ calls the scheduler while a signal is
pending. The task doesnâ€™t go through the usual blocking/waking and is set
back to runnable, the resulting switch (if there) looks like a yield to the
”…””}”(hjr  hžhhŸNh Nubj  )”}”(hŒ``signal_wakeup``”h]”hŒsignal_wakeup”…””}”(hjÐ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hjr  ubhŒ± state and is followed by the signal delivery. From this
state, the monitor expects a signal even if it sees a wakeup event, although
not necessary, to rule out false negatives.”…””}”(hjr  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h Mhjn  ubah}”(h]”h ]”h"]”h$]”h&]”uh1h¼hj{  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”j6  Œ*”uh1h·hŸh¶h M	hjJ  hžhubhÃ)”}”(hXœ  This monitor doesn't include a running state, ``sleepable`` and ``runnable``
are only referring to the task's desired state, which could be scheduled out
(e.g. due to preemption). However, it does include the event
``sched_switch_in`` to represent when a task is allowed to become running. This
can be triggered also by preemption, but cannot occur after the task got to
``sleeping`` before a ``wakeup`` occurs::”h]”(hŒ0This monitor doesnâ€™t include a running state, ”…””}”(hjõ  hžhhŸNh Nubj  )”}”(hŒ``sleepable``”h]”hŒ	sleepable”…””}”(hjý  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hjõ  ubhŒ and ”…””}”(hjõ  hžhhŸNh Nubj  )”}”(hŒ``runnable``”h]”hŒrunnable”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hjõ  ubhŒ
are only referring to the taskâ€™s desired state, which could be scheduled out
(e.g. due to preemption). However, it does include the event
”…””}”(hjõ  hžhhŸNh Nubj  )”}”(hŒ``sched_switch_in``”h]”hŒsched_switch_in”…””}”(hj!  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hjõ  ubhŒ‰ to represent when a task is allowed to become running. This
can be triggered also by preemption, but cannot occur after the task got to
”…””}”(hjõ  hžhhŸNh Nubj  )”}”(hŒ``sleeping``”h]”hŒsleeping”…””}”(hj3  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hjõ  ubhŒ
 before a ”…””}”(hjõ  hžhhŸNh Nubj  )”}”(hŒ
``wakeup``”h]”hŒwakeup”…””}”(hjE  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hjõ  ubhŒ occurs:”…””}”(hjõ  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h M$hjJ  hžhubjü  )”}”(hXü    +--------------------------------------------------------------------------+
  |                                                                          |
  |                                                                          |
  | switch_suspend           |                                               |
  | switch_blocking          |                                               |
  v                          v                                               |
+----------+              #==========================#   set_state_runnable  |
|          |              H                          H   wakeup              |
|          |              H                          H   switch_in           |
|          |              H                          H   switch_yield        |
| sleeping |              H                          H   switch_preempt      |
|          |              H                          H   signal_deliver      |
|          |  switch_     H                          H ------+               |
|          |  _blocking   H         runnable         H       |               |
|          | <----------- H                          H <-----+               |
+----------+              H                          H                       |
  |   wakeup              H                          H                       |
  +---------------------> H                          H                       |
                          H                          H                       |
              +---------> H                          H                       |
              |           #==========================#                       |
              |             |                ^                               |
              |             |                | set_state_runnable            |
              |             |                | wakeup                        |
              |    set_state_sleepable       |      +------------------------+
              |             v                |      |
              |           +--------------------------+  set_state_sleepable
              |           |                          |  switch_in
              |           |                          |  switch_preempt
  signal_deliver          |        sleepable         |  signal_deliver
              |           |                          | ------+
              |           |                          |       |
              |           |                          | <-----+
              |           +--------------------------+
              |             |                ^
              |        switch_yield          | set_state_sleepable
              |             v                |
              |           +---------------+  |
              +---------- | signal_wakeup | -+
                          +---------------+
                            ^           | switch_in
                            |           | switch_preempt
                            |           | switch_yield
                            +-----------+ wakeup”h]”hXü    +--------------------------------------------------------------------------+
  |                                                                          |
  |                                                                          |
  | switch_suspend           |                                               |
  | switch_blocking          |                                               |
  v                          v                                               |
+----------+              #==========================#   set_state_runnable  |
|          |              H                          H   wakeup              |
|          |              H                          H   switch_in           |
|          |              H                          H   switch_yield        |
| sleeping |              H                          H   switch_preempt      |
|          |              H                          H   signal_deliver      |
|          |  switch_     H                          H ------+               |
|          |  _blocking   H         runnable         H       |               |
|          | <----------- H                          H <-----+               |
+----------+              H                          H                       |
  |   wakeup              H                          H                       |
  +---------------------> H                          H                       |
                          H                          H                       |
              +---------> H                          H                       |
              |           #==========================#                       |
              |             |                ^                               |
              |             |                | set_state_runnable            |
              |             |                | wakeup                        |
              |    set_state_sleepable       |      +------------------------+
              |             v                |      |
              |           +--------------------------+  set_state_sleepable
              |           |                          |  switch_in
              |           |                          |  switch_preempt
  signal_deliver          |        sleepable         |  signal_deliver
              |           |                          | ------+
              |           |                          |       |
              |           |                          | <-----+
              |           +--------------------------+
              |             |                ^
              |        switch_yield          | set_state_sleepable
              |             v                |
              |           +---------------+  |
              +---------- | signal_wakeup | -+
                          +---------------+
                            ^           | switch_in
                            |           | switch_preempt
                            |           | switch_yield
                            +-----------+ wakeup”…””}”hj]  sbah}”(h]”h ]”h"]”h$]”h&]”j  j  uh1jû  hŸh¶h M+hjJ  hžhubeh}”(h]”Œmonitor-sssw”ah ]”h"]”Œmonitor sssw”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Mubh¢)”}”(hhh]”(h§)”}”(hŒMonitor opid”h]”hŒMonitor opid”…””}”(hjv  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjs  hžhhŸh¶h MYubhÃ)”}”(hX“  The operations with preemption and irq disabled (opid) monitor ensures
operations like ``wakeup`` and ``need_resched`` occur with interrupts and
preemption disabled or during interrupt context, in such case preemption may
not be disabled explicitly.
``need_resched`` can be set by some RCU internals functions, in which case it
doesn't match a task wakeup and might occur with only interrupts disabled::”h]”(hŒWThe operations with preemption and irq disabled (opid) monitor ensures
operations like ”…””}”(hj„  hžhhŸNh Nubj  )”}”(hŒ
``wakeup``”h]”hŒwakeup”…””}”(hjŒ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj„  ubhŒ and ”…””}”(hj„  hžhhŸNh Nubj  )”}”(hŒ``need_resched``”h]”hŒneed_resched”…””}”(hjž  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj„  ubhŒ„ occur with interrupts and
preemption disabled or during interrupt context, in such case preemption may
not be disabled explicitly.
”…””}”(hj„  hžhhŸNh Nubj  )”}”(hŒ``need_resched``”h]”hŒneed_resched”…””}”(hj°  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hj„  ubhŒŠ can be set by some RCU internals functions, in which case it
doesnâ€™t match a task wakeup and might occur with only interrupts disabled:”…””}”(hj„  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h M[hjs  hžhubjü  )”}”(hX-
                 |                     sched_need_resched
               |                     sched_waking
               |                     irq_entry
               |                   +--------------------+
               v                   v                    |
             +------------------------------------------------------+
+----------- |                     disabled                         | <+
|            +------------------------------------------------------+  |
|              |                 ^                                     |
|              |          preempt_disable      sched_need_resched      |
|       preempt_enable           |           +--------------------+    |
|              v                 |           v                    |    |
|            +------------------------------------------------------+  |
|            |                   irq_disabled                       |  |
|            +------------------------------------------------------+  |
|                              |             |        ^                |
|     irq_entry            irq_entry         |        |                |
|     sched_need_resched       v             |   irq_disable           |
|     sched_waking +--------------+          |        |                |
|           +----- |              |     irq_enable    |                |
|           |      |    in_irq    |          |        |                |
|           +----> |              |          |        |                |
|                  +--------------+          |        |          irq_disable
|                     |                      |        |                |
| irq_enable          | irq_enable           |        |                |
|                     v                      v        |                |
|            #======================================================#  |
|            H                     enabled                          H  |
|            #======================================================#  |
|              |                   ^         ^ preempt_enable     |    |
|       preempt_disable     preempt_enable   +--------------------+    |
|              v                   |                                   |
|            +------------------+  |                                   |
+----------> | preempt_disabled | -+                                   |
             +------------------+                                      |
               |                                                       |
               +-------------------------------------------------------+”h]”hX-
                 |                     sched_need_resched
               |                     sched_waking
               |                     irq_entry
               |                   +--------------------+
               v                   v                    |
             +------------------------------------------------------+
+----------- |                     disabled                         | <+
|            +------------------------------------------------------+  |
|              |                 ^                                     |
|              |          preempt_disable      sched_need_resched      |
|       preempt_enable           |           +--------------------+    |
|              v                 |           v                    |    |
|            +------------------------------------------------------+  |
|            |                   irq_disabled                       |  |
|            +------------------------------------------------------+  |
|                              |             |        ^                |
|     irq_entry            irq_entry         |        |                |
|     sched_need_resched       v             |   irq_disable           |
|     sched_waking +--------------+          |        |                |
|           +----- |              |     irq_enable    |                |
|           |      |    in_irq    |          |        |                |
|           +----> |              |          |        |                |
|                  +--------------+          |        |          irq_disable
|                     |                      |        |                |
| irq_enable          | irq_enable           |        |                |
|                     v                      v        |                |
|            #======================================================#  |
|            H                     enabled                          H  |
|            #======================================================#  |
|              |                   ^         ^ preempt_enable     |    |
|       preempt_disable     preempt_enable   +--------------------+    |
|              v                   |                                   |
|            +------------------+  |                                   |
+----------> | preempt_disabled | -+                                   |
             +------------------+                                      |
               |                                                       |
               +-------------------------------------------------------+”…””}”hjÈ  sbah}”(h]”h ]”h"]”h$]”h&]”j  j  uh1jû  hŸh¶h Mbhjs  hžhubhÃ)”}”(hXÆ  This monitor is designed to work on ``PREEMPT_RT`` kernels, the special case of
events occurring in interrupt context is a shortcut to identify valid scenarios
where the preemption tracepoints might not be visible, during interrupts
preemption is always disabled. On non- ``PREEMPT_RT`` kernels, the interrupts
might invoke a softirq to set ``need_resched`` and wake up a task. This is
another special case that is currently not supported by the monitor.”h]”(hŒ$This monitor is designed to work on ”…””}”(hjÖ  hžhhŸNh Nubj  )”}”(hŒ``PREEMPT_RT``”h]”hŒ
PREEMPT_RT”…””}”(hjÞ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hjÖ  ubhŒÞ kernels, the special case of
events occurring in interrupt context is a shortcut to identify valid scenarios
where the preemption tracepoints might not be visible, during interrupts
preemption is always disabled. On non- ”…””}”(hjÖ  hžhhŸNh Nubj  )”}”(hŒ``PREEMPT_RT``”h]”hŒ
PREEMPT_RT”…””}”(hjð  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hjÖ  ubhŒ7 kernels, the interrupts
might invoke a softirq to set ”…””}”(hjÖ  hžhhŸNh Nubj  )”}”(hŒ``need_resched``”h]”hŒneed_resched”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j
  hjÖ  ubhŒa and wake up a task. This is
another special case that is currently not supported by the monitor.”…””}”(hjÖ  hžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h Mˆhjs  hžhubeh}”(h]”Œmonitor-opid”ah ]”h"]”Œmonitor opid”ah$]”h&]”uh1h¡hh£hžhhŸh¶h MYubh¢)”}”(hhh]”(h§)”}”(hŒ
References”h]”hŒ
References”…””}”(hj%  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj"  hžhhŸh¶h MubhÃ)”}”(hŒ)[1] - https://bristot.me/linux-task-model”h]”(hŒ[1] - ”…””}”(hj3  hžhhŸNh Nubhû)”}”(hŒ#https://bristot.me/linux-task-model”h]”hŒ#https://bristot.me/linux-task-model”…””}”(hj;  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”Œrefuri”j=  uh1húhj3  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÂhŸh¶h M’hj"  hžhubeh}”(h]”Œ
references”ah ]”h"]”Œ
references”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Mubeh}”(h]”Œscheduler-monitors”ah ]”h"]”Œscheduler monitors”ah$]”h&]”uh1h¡hhhžhhŸh¶h Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”h¶uh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(h¦NŒ	generator”NŒ	datestamp”NŒsource_link”NŒ
source_url”NŒtoc_backlinks”Œentry”Œfootnote_backlinks”KŒsectnum_xform”KŒstrip_comments”NŒstrip_elements_with_classes”NŒstrip_classes”NŒreport_level”KŒ
halt_level”KŒexit_status_level”KŒdebug”NŒwarning_stream”NŒ	traceback”ˆŒinput_encoding”Œ	utf-8-sig”Œinput_encoding_error_handler”Œstrict”Œoutput_encoding”Œutf-8”Œoutput_encoding_error_handler”jƒ  Œerror_encoding”Œutf-8”Œerror_encoding_error_handler”Œbackslashreplace”Œlanguage_code”Œen”Œrecord_dependencies”NŒconfig”NŒ	id_prefix”hŒauto_id_prefix”Œid”Œdump_settings”NŒdump_internals”NŒdump_transforms”NŒdump_pseudo_xml”NŒexpose_internals”NŒstrict_visitor”NŒ_disable_config”NŒ_source”h¶Œ_destination”NŒ_config_files”]”Œ7/var/lib/git/docbuild/linux/Documentation/docutils.conf”aŒfile_insertion_enabled”ˆŒraw_enabled”KŒline_length_limit”M'Œpep_references”NŒpep_base_url”Œhttps://peps.python.org/”Œpep_file_url_template”Œpep-%04d”Œrfc_references”NŒrfc_base_url”Œ&https://datatracker.ietf.org/doc/html/”Œ	tab_width”KŒtrim_footnote_reference_space”‰Œsyntax_highlight”Œlong”Œsmart_quotes”ˆŒsmartquotes_locales”]”Œcharacter_level_inline_markup”‰Œdoctitle_xform”‰Œdocinfo_xform”KŒsectsubtitle_xform”‰Œimage_loading”Œlink”Œembed_stylesheet”‰Œcloak_email_addresses”ˆŒsection_self_link”‰Œenv”NubŒreporter”NŒindirect_targets”]”Œsubstitution_defs”}”Œsubstitution_names”}”Œrefnames”}”Œrefids”}”Œnameids”}”(j]  jZ  j¬  j©  jî  jë  j  j  jG  jD  j|  jy  j±  j®  jæ  jã  jG  jD  jp  jm  j  j  jU  jR  uŒ	nametypes”}”(j]  ‰j¬  ‰jî  ‰j  ‰jG  ‰j|  ‰j±  ‰jæ  ‰jG  ‰jp  ‰j  ‰jU  ‰uh}”(jZ  h£j©  j8  jë  j¯  j  jÜ  jD  j  jy  jJ  j®  j  jã  j´  jD  jñ  jm  jJ  j  js  jR  j"  uŒfootnote_refs”}”Œcitation_refs”}”Œautofootnotes”]”Œautofootnote_refs”]”Œsymbol_footnotes”]”Œsymbol_footnote_refs”]”Œ	footnotes”]”Œ	citations”]”Œautofootnote_start”KŒsymbol_footnote_start”K Œ
id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”Œtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
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