€•¿:      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Portuguese (Brazilian)”…””}”hh‚sbah}”(h]”h ]”h"]”h$]”h&]”Œ	refdomain”h)Œreftype”h+Œ	reftarget”Œ(/translations/pt_BR/scheduler/sched-arch”Œmodname”NŒ	classname”NŒrefexplicit”ˆuh1hhhubh)”}”(hhh]”hŒSpanish”…””}”hh–sbah}”(h]”h ]”h"]”h$]”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$]”h&]”Œcurrent_language”ŒEnglish”uh1h
hhŒ	_document”hŒsource”NŒline”NubhŒsection”“”)”}”(hhh]”(hŒtitle”“”)”}”(hŒACPU Scheduler implementation hints for architecture specific code”h]”hŒACPU Scheduler implementation hints for architecture specific code”…””}”(hh¼h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhh·h²hh³ŒB/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hÓh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÑh³hÊh´KhhÍubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´Khh·h²hubh¶)”}”(hhh]”(h»)”}”(hŒContext switch”h]”hŒContext switch”…””}”(hhêh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhhçh²hh³hÊh´KubhÒ)”}”(hŒô1. Runqueue locking
By default, the switch_to arch function is called with the runqueue
locked. This is usually not a problem unless switch_to may need to
take the runqueue lock. This is usually due to a wake up operation in
the context switch.”h]”hŒô1. Runqueue locking
By default, the switch_to arch function is called with the runqueue
locked. This is usually not a problem unless switch_to may need to
take the runqueue lock. This is usually due to a wake up operation in
the context switch.”…””}”(hhøh²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÑh³hÊh´K	hhçh²hubhÒ)”}”(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j  h²hh³Nh´NubhŒtitle_reference”“”)”}”(hŒ$`#define __ARCH_WANT_UNLOCKED_CTXSW`”h]”hŒ"#define __ARCH_WANT_UNLOCKED_CTXSW”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj  ubhŒA in a header file
(typically the one where switch_to is defined).”…””}”(hj  h²hh³Nh´Nubeh}”(h]”h ]”h"]”h$]”h&]”uh1hÑh³hÊh´Khhçh²hubhÒ)”}”(hŒ†Unlocked context switches introduce only a very minor performance
penalty to the core scheduler implementation in the CONFIG_SMP case.”h]”hŒ†Unlocked context switches introduce only a very minor performance
penalty to the core scheduler implementation in the CONFIG_SMP case.”…””}”(hj(  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÑh³hÊh´Khhçh²hubeh}”(h]”Œcontext-switch”ah ]”h"]”Œcontext switch”ah$]”h&]”uh1hµhh·h²hh³hÊh´Kubh¶)”}”(hhh]”(h»)”}”(hŒCPU idle”h]”hŒCPU idle”…””}”(hjA  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhj>  h²hh³hÊh´KubhÒ)”}”(hŒ8Your cpu_idle routines need to obey the following rules:”h]”hŒ8Your cpu_idle routines need to obey the following rules:”…””}”(hjO  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÑh³hÊh´Khj>  h²hubhŒenumerated_list”“”)”}”(hhh]”(hŒ	list_item”“”)”}”(hŒoPreempt should now disabled over idle routines. Should only
be enabled to call schedule() then disabled again.
”h]”hÒ)”}”(hŒnPreempt should now disabled over idle routines. Should only
be enabled to call schedule() then disabled again.”h]”hŒnPreempt should now disabled over idle routines. Should only
be enabled to call schedule() then disabled again.”…””}”(hjh  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÑh³hÊh´Khjd  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jb  hj_  h²hh³hÊh´Nubjc  )”}”(hŒÇneed_resched/TIF_NEED_RESCHED is only ever set, and will never
be cleared until the running task has called schedule(). Idle
threads need only ever query need_resched, and may never set or
clear it.
”h]”hÒ)”}”(hŒÆneed_resched/TIF_NEED_RESCHED is only ever set, and will never
be cleared until the running task has called schedule(). Idle
threads need only ever query need_resched, and may never set or
clear it.”h]”hŒÆneed_resched/TIF_NEED_RESCHED is only ever set, and will never
be cleared until the running task has called schedule(). Idle
threads need only ever query need_resched, and may never set or
clear it.”…””}”(hj€  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÑh³hÊh´Khj|  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jb  hj_  h²hh³hÊh´Nubjc  )”}”(hŒtWhen cpu_idle finds (need_resched() == 'true'), it should call
schedule(). It should not call schedule() otherwise.
”h]”hÒ)”}”(hŒsWhen cpu_idle finds (need_resched() == 'true'), it should call
schedule(). It should not call schedule() otherwise.”h]”hŒwWhen cpu_idle finds (need_resched() == â€˜trueâ€™), it should call
schedule(). It should not call schedule() otherwise.”…””}”(hj˜  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÑh³hÊh´K"hj”  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jb  hj_  h²hh³hÊh´Nubjc  )”}”(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]”(hÒ)”}”(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j°  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÑh³hÊh´K%hj¬  ubhÌ)”}”(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]”(hÒ)”}”(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jÂ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÑh³hÊh´K*hj¾  ubhŒliteral_block”“”)”}”(hŒ§local_irq_disable();
if (!need_resched()) {
        local_irq_enable();
        *** resched interrupt arrives here ***
        __asm__("sleep until next interrupt");
}”h]”hŒ§local_irq_disable();
if (!need_resched()) {
        local_irq_enable();
        *** resched interrupt arrives here ***
        __asm__("sleep until next interrupt");
}”…””}”hjÒ  sbah}”(h]”h ]”h"]”h$]”h&]”Œ	xml:space”Œpreserve”uh1jÐ  h³hÊh´K,hj¾  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´K*hj¬  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jb  hj_  h²hh³hÊh´Nubjc  )”}”(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]”(hÒ)”}”(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jò  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÑh³hÊh´K3hjî  ubhÌ)”}”(hŒÞ- 5a. If TIF_POLLING_NRFLAG is set, and we do decide to enter
  an interrupt sleep, it needs to be cleared then a memory
  barrier issued (followed by a test of need_resched with
  interrupts disabled, as explained in 3).
”h]”hŒbullet_list”“”)”}”(hhh]”jc  )”}”(hŒÖ5a. If TIF_POLLING_NRFLAG is set, and we do decide to enter
an interrupt sleep, it needs to be cleared then a memory
barrier issued (followed by a test of need_resched with
interrupts disabled, as explained in 3).
”h]”hÒ)”}”(hŒÕ5a. If TIF_POLLING_NRFLAG is set, and we do decide to enter
an interrupt sleep, it needs to be cleared then a memory
barrier issued (followed by a test of need_resched with
interrupts disabled, as explained in 3).”h]”hŒÕ5a. If TIF_POLLING_NRFLAG is set, and we do decide to enter
an interrupt sleep, it needs to be cleared then a memory
barrier issued (followed by a test of need_resched with
interrupts disabled, as explained in 3).”…””}”(hj  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÑh³hÊh´K9hj	  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jb  hj  ubah}”(h]”h ]”h"]”h$]”h&]”Œbullet”Œ-”uh1j  h³hÊh´K9hj   ubah}”(h]”h ]”h"]”h$]”h&]”uh1hËh³hÊh´K9hjî  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jb  hj_  h²hh³hÊh´Nubeh}”(h]”h ]”h"]”h$]”h&]”Œenumtype”Œarabic”Œprefix”hŒsuffix”Œ.”uh1j]  hj>  h²hh³hÊh´KubhÒ)”}”(hŒSarch/x86/kernel/process.c has examples of both polling and
sleeping idle functions.”h]”hŒSarch/x86/kernel/process.c has examples of both polling and
sleeping idle functions.”…””}”(hj@  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÑh³hÊh´K>hj>  h²hubeh}”(h]”Œcpu-idle”ah ]”h"]”Œcpu idle”ah$]”h&]”uh1hµhh·h²hh³hÊh´Kubh¶)”}”(hhh]”(h»)”}”(hŒPossible arch/ problems”h]”hŒPossible arch/ problems”…””}”(hjY  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hºhjV  h²hh³hÊh´KCubhÒ)”}”(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jg  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÑh³hÊh´KEhjV  h²hubhŒdefinition_list”“”)”}”(hhh]”hŒdefinition_list_item”“”)”}”(hŒ}sparc - IRQs on at this point(?), change local_irq_save to _disable.
- TODO: needs secondary CPUs to disable preempt (See #1)”h]”(hŒterm”“”)”}”(hŒDsparc - IRQs on at this point(?), change local_irq_save to _disable.”h]”hŒDsparc - IRQs on at this point(?), change local_irq_save to _disable.”…””}”(hj‚  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1j€  h³hÊh´KGhj|  ubhŒ
definition”“”)”}”(hhh]”j  )”}”(hhh]”jc  )”}”(hŒ6TODO: needs secondary CPUs to disable preempt (See #1)”h]”hÒ)”}”(hjš  h]”hŒ6TODO: needs secondary CPUs to disable preempt (See #1)”…””}”(hjœ  h²hh³Nh´Nubah}”(h]”h ]”h"]”h$]”h&]”uh1hÑh³hÊh´KHhj˜  ubah}”(h]”h ]”h"]”h$]”h&]”uh1jb  hj•  ubah}”(h]”h ]”h"]”h$]”h&]”j'  j(  uh1j  h³hÊh´KHhj’  ubah}”(h]”h ]”h"]”h$]”h&]”uh1j  hj|  ubeh}”(h]”h ]”h"]”h$]”h&]”uh1jz  h³hÊh´KGhjw  ubah}”(h]”h ]”h"]”h$]”h&]”uh1ju  hjV  h²hh³Nh´Nubeh}”(h]”Œpossible-arch-problems”ah ]”h"]”Œpossible arch/ problems”ah$]”h&]”uh1hµhh·h²hh³hÊh´KCubeh}”(h]”ŒAcpu-scheduler-implementation-hints-for-architecture-specific-code”ah ]”h"]”ŒAcpu scheduler implementation hints for architecture specific code”ah$]”h&]”uh1hµhhh²hh³hÊh´Kubeh}”(h]”h ]”h"]”h$]”h&]”Œsource”hÊuh1hŒcurrent_source”NŒcurrent_line”NŒsettings”Œdocutils.frontend”ŒValues”“”)”}”(hºNŒ	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”jú  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”hÊŒ_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”}”(jÔ  jÑ  j;  j8  jS  jP  jÌ  jÉ  uŒ	nametypes”}”(jÔ  ‰j;  ‰jS  ‰jÌ  ‰uh}”(jÑ  h·j8  hçjP  j>  jÉ  jV  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
decoration”Nh²hub.