€•Ü9      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/scheduler/sched-arch”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$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ(/translations/zh_TW/scheduler/sched-arch”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒItalian”…””}”hhFsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ(/translations/it_IT/scheduler/sched-arch”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒJapanese”…””}”hhZsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ(/translations/ja_JP/scheduler/sched-arch”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒKorean”…””}”hhnsbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ(/translations/ko_KR/scheduler/sched-arch”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ(/translations/sp_SP/scheduler/sched-arch”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubeh}”(h]”h ]”h"]”h$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒACPU Scheduler implementation hints for architecture specific code”h]”hŒACPU Scheduler implementation hints for architecture specific code”…””}”(hh¨hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hh£hžhhŸŒB/var/lib/git/docbuild/linux/Documentation/scheduler/sched-arch.rst”h KubhŒblock_quote”“”)”}”(hŒNick Piggin, 2005
”h]”hŒ	paragraph”“”)”}”(hŒNick Piggin, 2005”h]”hŒNick Piggin, 2005”…””}”(hh¿hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h Khh¹ubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h Khh£hžhubh¢)”}”(hhh]”(h§)”}”(hŒContext switch”h]”hŒContext switch”…””}”(hhÖhžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hhÓhžhhŸh¶h Kubh¾)”}”(hŒô1. Runqueue locking
By default, the switch_to arch function is called with the runqueue
locked. This is usually not a problem unless switch_to may need to
take the runqueue lock. This is usually due to a wake up operation in
the context switch.”h]”hŒô1. Runqueue locking
By default, the switch_to arch function is called with the runqueue
locked. This is usually not a problem unless switch_to may need to
take the runqueue lock. This is usually due to a wake up operation in
the context switch.”…””}”(hhähžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K	hhÓhžhubh¾)”}”(hŒ²To request the scheduler call switch_to with the runqueue unlocked,
you must `#define __ARCH_WANT_UNLOCKED_CTXSW` in a header file
(typically the one where switch_to is defined).”h]”(hŒMTo request the scheduler call switch_to with the runqueue unlocked,
you must ”…””}”(hhòhžhhŸNh NubhŒtitle_reference”“”)”}”(hŒ$`#define __ARCH_WANT_UNLOCKED_CTXSW`”h]”hŒ"#define __ARCH_WANT_UNLOCKED_CTXSW”…””}”(hhühžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1húhhòubhŒA in a header file
(typically the one where switch_to is defined).”…””}”(hhòhžhhŸNh Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h KhhÓhžhubh¾)”}”(hŒ†Unlocked context switches introduce only a very minor performance
penalty to the core scheduler implementation in the CONFIG_SMP case.”h]”hŒ†Unlocked context switches introduce only a very minor performance
penalty to the core scheduler implementation in the CONFIG_SMP case.”…””}”(hj  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h KhhÓhžhubeh}”(h]”Œcontext-switch”ah ]”h"]”Œcontext switch”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Kubh¢)”}”(hhh]”(h§)”}”(hŒCPU idle”h]”hŒCPU idle”…””}”(hj-  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hj*  hžhhŸh¶h Kubh¾)”}”(hŒ8Your cpu_idle routines need to obey the following rules:”h]”hŒ8Your cpu_idle routines need to obey the following rules:”…””}”(hj;  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h Khj*  hžhubhŒenumerated_list”“”)”}”(hhh]”(hŒ	list_item”“”)”}”(hŒoPreempt should now disabled over idle routines. Should only
be enabled to call schedule() then disabled again.
”h]”h¾)”}”(hŒnPreempt should now disabled over idle routines. Should only
be enabled to call schedule() then disabled again.”h]”hŒnPreempt should now disabled over idle routines. Should only
be enabled to call schedule() then disabled again.”…””}”(hjT  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h KhjP  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jN  hjK  hžhhŸh¶h NubjO  )”}”(hŒÇneed_resched/TIF_NEED_RESCHED is only ever set, and will never
be cleared until the running task has called schedule(). Idle
threads need only ever query need_resched, and may never set or
clear it.
”h]”h¾)”}”(hŒÆneed_resched/TIF_NEED_RESCHED is only ever set, and will never
be cleared until the running task has called schedule(). Idle
threads need only ever query need_resched, and may never set or
clear it.”h]”hŒÆneed_resched/TIF_NEED_RESCHED is only ever set, and will never
be cleared until the running task has called schedule(). Idle
threads need only ever query need_resched, and may never set or
clear it.”…””}”(hjl  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h Khjh  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jN  hjK  hžhhŸh¶h NubjO  )”}”(hŒtWhen cpu_idle finds (need_resched() == 'true'), it should call
schedule(). It should not call schedule() otherwise.
”h]”h¾)”}”(hŒsWhen cpu_idle finds (need_resched() == 'true'), it should call
schedule(). It should not call schedule() otherwise.”h]”hŒwWhen cpu_idle finds (need_resched() == â€˜trueâ€™), it should call
schedule(). It should not call schedule() otherwise.”…””}”(hj„  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K"hj€  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jN  hjK  hžhhŸh¶h NubjO  )”}”(hX  The only time interrupts need to be disabled when checking
need_resched is if we are about to sleep the processor until
the next interrupt (this doesn't provide any protection of
need_resched, it prevents losing an interrupt):

     4a. Common problem with this type of sleep appears to be::

             local_irq_disable();
             if (!need_resched()) {
                     local_irq_enable();
                     *** resched interrupt arrives here ***
                     __asm__("sleep until next interrupt");
             }
”h]”(h¾)”}”(hŒâThe only time interrupts need to be disabled when checking
need_resched is if we are about to sleep the processor until
the next interrupt (this doesn't provide any protection of
need_resched, it prevents losing an interrupt):”h]”hŒäThe only time interrupts need to be disabled when checking
need_resched is if we are about to sleep the processor until
the next interrupt (this doesnâ€™t provide any protection of
need_resched, it prevents losing an interrupt):”…””}”(hjœ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K%hj˜  ubh¸)”}”(hX  4a. Common problem with this type of sleep appears to be::

        local_irq_disable();
        if (!need_resched()) {
                local_irq_enable();
                *** resched interrupt arrives here ***
                __asm__("sleep until next interrupt");
        }
”h]”(h¾)”}”(hŒ:4a. Common problem with this type of sleep appears to be::”h]”hŒ94a. Common problem with this type of sleep appears to be:”…””}”(hj®  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K*hjª  ubhŒliteral_block”“”)”}”(hŒ§local_irq_disable();
if (!need_resched()) {
        local_irq_enable();
        *** resched interrupt arrives here ***
        __asm__("sleep until next interrupt");
}”h]”hŒ§local_irq_disable();
if (!need_resched()) {
        local_irq_enable();
        *** resched interrupt arrives here ***
        __asm__("sleep until next interrupt");
}”…””}”hj¾  sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1j¼  hŸh¶h K,hjª  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K*hj˜  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jN  hjK  hžhhŸh¶h NubjO  )”}”(hXû  TIF_POLLING_NRFLAG can be set by idle routines that do not
need an interrupt to wake them up when need_resched goes high.
In other words, they must be periodically polling need_resched,
although it may be reasonable to do some background work or enter
a low CPU priority.

   - 5a. If TIF_POLLING_NRFLAG is set, and we do decide to enter
     an interrupt sleep, it needs to be cleared then a memory
     barrier issued (followed by a test of need_resched with
     interrupts disabled, as explained in 3).
”h]”(h¾)”}”(hX  TIF_POLLING_NRFLAG can be set by idle routines that do not
need an interrupt to wake them up when need_resched goes high.
In other words, they must be periodically polling need_resched,
although it may be reasonable to do some background work or enter
a low CPU priority.”h]”hX  TIF_POLLING_NRFLAG can be set by idle routines that do not
need an interrupt to wake them up when need_resched goes high.
In other words, they must be periodically polling need_resched,
although it may be reasonable to do some background work or enter
a low CPU priority.”…””}”(hjÞ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K3hjÚ  ubh¸)”}”(hŒÞ- 5a. If TIF_POLLING_NRFLAG is set, and we do decide to enter
  an interrupt sleep, it needs to be cleared then a memory
  barrier issued (followed by a test of need_resched with
  interrupts disabled, as explained in 3).
”h]”hŒbullet_list”“”)”}”(hhh]”jO  )”}”(hŒÖ5a. If TIF_POLLING_NRFLAG is set, and we do decide to enter
an interrupt sleep, it needs to be cleared then a memory
barrier issued (followed by a test of need_resched with
interrupts disabled, as explained in 3).
”h]”h¾)”}”(hŒÕ5a. If TIF_POLLING_NRFLAG is set, and we do decide to enter
an interrupt sleep, it needs to be cleared then a memory
barrier issued (followed by a test of need_resched with
interrupts disabled, as explained in 3).”h]”hŒÕ5a. If TIF_POLLING_NRFLAG is set, and we do decide to enter
an interrupt sleep, it needs to be cleared then a memory
barrier issued (followed by a test of need_resched with
interrupts disabled, as explained in 3).”…””}”(hjù  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K9hjõ  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jN  hjò  ubah}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ-”uh1jð  hŸh¶h K9hjì  ubah}”(h]”h ]”h"]”h$]”h&]”uh1h·hŸh¶h K9hjÚ  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jN  hjK  hžhhŸh¶h Nubeh}”(h]”h ]”h"]”h$]”h&]”Œenumtype”Œarabic”Œprefix”hŒsuffix”Œ.”uh1jI  hj*  hžhhŸh¶h Kubh¾)”}”(hŒSarch/x86/kernel/process.c has examples of both polling and
sleeping idle functions.”h]”hŒSarch/x86/kernel/process.c has examples of both polling and
sleeping idle functions.”…””}”(hj,  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h K>hj*  hžhubeh}”(h]”Œcpu-idle”ah ]”h"]”Œcpu idle”ah$]”h&]”uh1h¡hh£hžhhŸh¶h Kubh¢)”}”(hhh]”(h§)”}”(hŒPossible arch/ problems”h]”hŒPossible arch/ problems”…””}”(hjE  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h¦hjB  hžhhŸh¶h KCubh¾)”}”(hŒCPossible arch problems I found (and either tried to fix or didn't):”h]”hŒEPossible arch problems I found (and either tried to fix or didnâ€™t):”…””}”(hjS  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h KEhjB  hžhubhŒdefinition_list”“”)”}”(hhh]”hŒdefinition_list_item”“”)”}”(hŒ}sparc - IRQs on at this point(?), change local_irq_save to _disable.
- TODO: needs secondary CPUs to disable preempt (See #1)”h]”(hŒterm”“”)”}”(hŒDsparc - IRQs on at this point(?), change local_irq_save to _disable.”h]”hŒDsparc - IRQs on at this point(?), change local_irq_save to _disable.”…””}”(hjn  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1jl  hŸh¶h KGhjh  ubhŒ
definition”“”)”}”(hhh]”jñ  )”}”(hhh]”jO  )”}”(hŒ6TODO: needs secondary CPUs to disable preempt (See #1)”h]”h¾)”}”(hj†  h]”hŒ6TODO: needs secondary CPUs to disable preempt (See #1)”…””}”(hjˆ  hžhhŸNh Nubah}”(h]”h ]”h"]”h$]”h&]”uh1h½hŸh¶h KHhj„  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jN  hj  ubah}”(h]”h ]”h"]”h$]”h&]”j  j  uh1jð  hŸh¶h KHhj~  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j|  hjh  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jf  hŸh¶h KGhjc  ubah}”(h]”h ]”h"]”h$]”h&]”uh1ja  hjB  hžhhŸNh Nubeh}”(h]”Œpossible-arch-problems”ah ]”h"]”Œpossible arch/ problems”ah$]”h&]”uh1h¡hh£hžhhŸh¶h KCubeh}”(h]”ŒAcpu-scheduler-implementation-hints-for-architecture-specific-code”ah ]”h"]”ŒAcpu scheduler implementation hints for architecture specific code”ah$]”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
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id_counter”Œcollections”ŒCounter”“”}”…”R”Œparse_messages”]”Œtransform_messages”]”Œtransformer”NŒinclude_log”]”Œ
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