limitedwww.ccc64.com

ELCEurope2018GengyourpatchesintomainlineLinuxWhatnottodo(andafewthingsyoucouldtryinstead)MarcZyngierOctober22,20182018ArmLimitedOpeningcreditsBeenmessingwiththeLinuxkernelsince1993PleaseblameStéphaneEranian.
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Firstpatchesmergedin1996(mddriver)Don'temailmeifyourdiskarraygetscorrupted.
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Ooadedmaintainershipin1997WithARMsince2010Tryingtobridgearchitecture,hardware,andobviouslyLinuxLookingaerKVM/armtogetherwithChristoerDallIRQsubsystemtogetherwithThomasGleixner22018ArmLimitedDisclaimerThisisn'tamaintainerrant!
ThistalkisforEVERYONE!
DoesnotonlyapplytorstmecontributorsThereissomethingforlongmehackersaswell!
NotallmaintainerswillagreewithmeIfyougetamedfordoinganyofthis,sendthemmyway!
32018ArmLimitedRecurrentthemesThereisabitofadisconnectbetweencontributorsandmaintainers:42018ArmLimitedRecurrentthemesThereisabitofadisconnectbetweencontributorsandmaintainers:"Mypatchesarebeingignored"42018ArmLimitedRecurrentthemesThereisabitofadisconnectbetweencontributorsandmaintainers:"Mypatchesarebeingignored""Ihavepostedthesepatches4mes,andtheyaresllnotmerged"42018ArmLimitedRecurrentthemesThereisabitofadisconnectbetweencontributorsandmaintainers:"Mypatchesarebeingignored""Ihavepostedthesepatches4mes,andtheyaresllnotmerged""I'vecopiedthiscodefromamainlinedriver,andyou'retellingmeitisn'tright"42018ArmLimitedRecurrentthemesThereisabitofadisconnectbetweencontributorsandmaintainers:"Mypatchesarebeingignored""Ihavepostedthesepatches4mes,andtheyaresllnotmerged""I'vecopiedthiscodefromamainlinedriver,andyou'retellingmeitisn'tright""Ionlywantthiscodemerged,Idon'thavethemetodoallthisextrawork"42018ArmLimitedRecurrentthemesThereisabitofadisconnectbetweencontributorsandmaintainers:"Mypatchesarebeingignored""Ihavepostedthesepatches4mes,andtheyaresllnotmerged""I'vecopiedthiscodefromamainlinedriver,andyou'retellingmeitisn'tright""Ionlywantthiscodemerged,Idon'thavethemetodoallthisextrawork""ButI'mgivingyouthiscodeforfree,whyaren'tyoujusttakingit"42018ArmLimitedRecurrentthemesThereisabitofadisconnectbetweencontributorsandmaintainers:"Mypatchesarebeingignored""Ihavepostedthesepatches4mes,andtheyaresllnotmerged""I'vecopiedthiscodefromamainlinedriver,andyou'retellingmeitisn'tright""Ionlywantthiscodemerged,Idon'thavethemetodoallthisextrawork""ButI'mgivingyouthiscodeforfree,whyaren'tyoujusttakingit""Idon'thavethemetounderstandthis,justtellmewhatIshouldwrite"42018ArmLimitedThecharacters52018ArmLimitedTheContributorSubmitsachangetothemainlinekernelsourceIntendstogetitmergedeventuallyCanbeanewfeatureabugxcodecleanupComplexityofthechangesrangesfromtrivialtobrain-melngThecontributorisoentheonewhounderstandstheproblembest62018ArmLimitedTheReviewerCanbedisnctfromthemaintainerOenothercontributorsSpreadstheload,sothatmaintainersdoscaleProbablytheleastrecognised,andyetoneofthemostimportantcharactersinthisstory72018ArmLimitedTheMaintainerThemaintainersareresponsibleforsomepieceofcodeinthekernel:nottobreaktobesecurereadable,understandableUlmatelytheoneswhoputtheirneckonthelineSpendanawfullotofmereviewingotherpeople'scodeOenthetargetofhundredsofemailsaday82018ArmLimitedMovaonsThesecharactershavequiteafewthingsincommon:Meengatasinglepointofcontenon:thecodeTryingtosolvedicultproblemsIndividualresponsibility,personalinvestmentVeryoennottheirmainjobQuiteoenacontributorgrowsintoareviewer,andthenamaintainer92018ArmLimitedTheplot102018ArmLimitedThekernelsubmissionworkowYouhavewrienpatchesforawickedidea:PostapatchseriesGetitreviewedRespondtocommentsRinse,repeatLookssimple,butthereisalotbehindthis.
112018ArmLimitedThekernelsubmissionworkowYouhavewrienpatchesforawickedidea:PostapatchseriesGetitreviewedRespondtocommentsRinse,repeatLookssimple,butthereisalotbehindthis.
Whatisthat"patchseries"thingWhodoIsendittoHowdoIgetitreviewedIdon'tunderstandthesecommentsandotherrequests.
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112018ArmLimitedThekernelsubmissionworkowYouhavewrienpatchesforawickedidea:PostapatchseriesGetitreviewedRespondtocommentsRinse,repeatLookssimple,butthereisalotbehindthis.
Whatisthat"patchseries"thingWhodoIsendittoHowdoIgetitreviewedIdon'tunderstandthesecommentsandotherrequestsCanbeoverwhelming112018ArmLimitedWhatisapatchseriesItisanorderedsetofpatchesItisconceptuallyasinglechangeSplitintomulplepatchesSplingpatchesisahardtopicNothinginthekernelbreaksatanypointinthemiddleoftheseriesWehavealimitedcapacitytoprocesshugechangesinonego122018ArmLimitedWhatdoesapatchserieslooklikeEachpatchhasatleandaclearcommitmessageEachpatchisnumberedx/n(patchnumberxoutofn)Wherexisunique,nisconstantacrosstheseries,andx<=nIthasauniqueversionnumberforthewholeseriesDonotpostaserieswiththesameversionnumbertwice!
Ithasacoverleer,numbered0/nUsuallyonlyifthereismorethanasinglepatchThecoverleerdescribethegoaloftheseriesandcontainsachangelogItcontainsadi-statofthewholeseriesAllthepatchesintheseriesareinreplytothecoverleer132018ArmLimitedWhytheserequirementsFromamaintainerorreviewerpointofview,theserequirementsarecrucial:Ordered:AllowsthereviewertoseeaprogressioninthedesignNeededforbiseconLogicalchanges:MulplethingschangingatoncemakethingshardtoreviewPatchnumbering:AmImissinganypatchinthisseriesHelpswiththeordering/threadinginanemailclientVersionnumbering:IsthissomethingnewOrhasitbeenreviewedalreadyDon'treplywithasinglepatchwithanewversionnumberCoverleer:SoyouknowwhatchangedfromonerevisiontoanotherMakesurealltherecipientsoftheseriesreceivethecoverleerAchancetohavingaconversaonwiththemaintainers142018ArmLimitedPatchseries:Don'tdothatIfyou'reabouttosendsomethingthatmayenduplookinglikethis:(Mon)18:58[Anonymous]RESEND[PATCHv510/12]arm64:vdso:replacegettimeofday.
Swithglobalvgettimeofday.
C(Mon)18:58[Anonymous]RESEND[PATCHv31/3]arm64:compat:Splitthesigreturntrampolinesandkuserhelpers(Csources)(Mon)18:58[Anonymous]RESEND[PATCHv32/3]arm64:compat:Splitthesigreturntrampolinesandkuserhelpers(assembler.
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(Mon)18:58[Anonymous]RESEND[PATCHv33/3]arm64:compat:AddCONFIG_KUSER_HELPERS(Mon)18:58[Anonymous]RESEND[PATCH]arm64:compat:Exposeoffsettoregistersinsigframes(Mon)18:58[Anonymous]RESEND[PATCHv26/6]arm64:WireupandexposethenewcompatvDSO.
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pleasedon't.
TryingtomakesenseofthisseriesisjusttoohardProbablymissingonsomeverygoodcodeThisisanetlossforthekernel152018ArmLimitedUsethetools,Lukegitisreallytheonlytoolyouneedandthereisnolifeworthlivingoutsideofgit.
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AlthoughyoucanusesometoolontopofgititselfButreally,youdon'tneedthatDonotsendpatchseriesbyhand.
Ever.
One-oconguraon:ConguregitasanemailclientSetsendmail.
tocover=1,sendmail.
cccover=1in~/.
gitconfigForeachseriesyouwanttosend:Idenfytherecipientsforthisseries.
Usescripts/get_maintainers.
plgitformat-patch-opatches/blah-v3--cover-letterv4.
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HEADEditpatches/blah/v3-0000-cover-letter.
patch,addingtherecipientsinyourcoverleergitsend-email--dry-runpatches/blah/v3-*patchIfitlooksgood,dropthe--dry-runandletitroll162018ArmLimitedUsingemailPleaseusethecanonicalemailequeewhenposngorresponding:Plaintextemailonly,noHTMLReplyinline,nottop-posngAvoidaachementsifatallpossibleNosillydisclaimer(thisisapublicmailinglist!
)CcpeoplewhenitmaersKeeptheCclistshortTrimtheemailyou'rerespondingtotheessenalcontext172018ArmLimitedDigression:whyemail"Whydoyouusethissillyoutdatedtechnologyinsteadof[web-thing-of-the-week]"Well,emailis:Mul-plaormArchivedAvailableoineNotinteracveDistributedEasytointegratewithgitandCIGengridofemailwouldrequireanewsystemtosasfytheseproperes.
Ofcourse,quiteafeworganisaoncannotdoemailproperly.
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That'savalidconcernAlotofpeopleareusingtheirpersonalemailforthisELCtalkideafornextyear:SMTPinaXXXXhoslecorporateenvironment182018ArmLimitedOfreviewersandbandwidthYou'vepostedapatchseriestwodaysagoandquicklyreceivedsomecommentsYou'vequicklyaddressedthose,collectedalltheAcksandreviewtags.
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andnoweagerpostanewversionNowtakeadeepbreath.
Giveachancetootherreviewerstocatchupwithyourwork.
Posngtoooenisusuallycounter-producveOnlyresultsinaDoSonthereviewer(youdon'twantthat)Allowaboutaweekbetweeneachversion,unlessaskedforanimmediaterespinRememberhowlongittookyoutowritethesepatchesReviewingthemwon'tbeanyquicker192018ArmLimitedScreenplay202018ArmLimitedThemaintainer/reviewerworkowIsitsomethingI'minterestedinormaintainDoesthepatchseriesmakesenseIsthereanyreportedfailureFixorfeaturePriorisaonEachmaintainerorreviewerhasspecicrequirementsNosuchthingasOneSieFitsAll212018ArmLimitedThemaintainer/reviewerworkowIsitsomethingI'minterestedinormaintainDoesthepatchseriesmakesenseIsthereanyreportedfailureFixorfeaturePriorisaonEachmaintainerorreviewerhasspecicrequirementsNosuchthingasOneSieFitsAllButthereissomethingthatinuencestheabove:TrustThisishowwerecognisecontributorsandreviewersMostoenpeoplewhogotheextramileWhenareviewerormaintainerasksforsomeextraworkonapatchseriesItisnottoannoythecontributorItistoimprovetheoverallqualityofthekernelitselfEventuallytobuildtrustbetweenthetwopares212018ArmLimitedWhytrustThisishowtheoverallpatchmergingmodelworks.
Thereistrustbetween:Linusandthetop-levelmaintainerstoplevelmaintainersandtheirsub-maintainersco-maintainersofasinglesubsystemIntheend,thistrustisjustasimportantasthecode.
Asowareprojectthatdoesn'tencouragecontribuonsdiesOneofmaintainers'roleistoretainthebestcontributorsWealwaysneednewreviewersandco-maintainersThebestcontribuonsbenetthelargestpartofthecommunityThisrequiresinvolvementofallpares222018ArmLimitedBuildingtrustAmaintainerorreviewercanaskyoutodosomeaddionalwork:ProvideabeerinfrastructureRefactorcodetolimitduplicaonMovebitsofafeaturetocorecodeTrytostepawayfromyourowncodeforawhile.
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SeehowthisrequesttsintotheoverallkernelIftherequestisunclear,askforclaricaon!
Ifyouthinkthisisn'tjused,trytocomeupwithyourownproposalThemaintainerisnotalwaysright,givethemanalternaveperspecveBecomethetrustedmaintainerofyourowncode!
232018ArmLimitedDigression:Drive-bypatchingOne-ocontribuonsContributornevertobeseenagainSomemesthekernelequivalentof"y-pping"Seetheabove"usttakeitalready"WedonotwanttodiscouragethisAnumberofbugxescomefromthoseone-osSomeotherarejustabunchofunmaintainablechangesWe'dalsoliketoconvincethesepeopletosckaround.
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Aerall,weallstartedwiththisrstpatch.
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ItisunclearhowwecanincenvisethesecontributorstoLookforanotherissuetoxHaveamoreconnuedengagementwiththekernelcommunity242018ArmLimitedBecomingareviewerOneofbestwaytoimproveyourkernel-fooistoreviewpatchesPicksomethingyou'reinterestedinYoudon'thavetobeanexpertinthedomainYoujustneedtobeabletofollowthecodeIfsomethingseemsunclear,askquesons!
Ifyouspotaproblem,sayso!
Ifyou'resasedwiththewaythecodelooks:Oponallyprovidea"Reviewed-by"Rememberthatyou'rereviewing"tothebestofyourability"Evenifyou'renotprovidingatag,yourinputisvaluable252018ArmLimitedBeyourrstreviewerBeforeyou'reabouttosendapatchseries:ReadyourownpatchesImeanit!
Really!
ThisisthebestwaytocatchbasicmistakesPutyourselfinthereviewer'sshoesDoesthiscodemakesenseIsitsplitinacoherentwayIsitcommented,documentedwellenoughHaveyoutakenallthereviewitemsintoaccountHaveyoucollectedalltheAcked-by:andReviewed-by:tagsIfyou'veanswered"yes"toalltheabove,shipit!
262018ArmLimitedClosingcommentsContribungtotheLinuxkernelisbothtoughandrewardingWearealltryingtoworktogetheronchangingsomepartofacode-baseUnderstandingeachother'spointofviewiskey–butcanbereallyhardBuildingaleveloftrustandunderstandingmakeseverythingeasierWehavetoolsandprocessesforgoodreasons–wearenotjusttryingtobedicult.
Honestly.
Askmeanythingifyou'reindoubt.
Pleasetrustmetobefriendly.
272018ArmLimitedThankyouTheArmtrademarksfeaturedinthispresentaonareregisteredtrademarksortrademarksofArmLimited(oritssubsidiaries)intheUSand/orelsewhere.
Allrightsreserved.
Allothermarksfeaturedmaybetrademarksoftheirrespecveowners.
www.
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com/company/policies/trademarks2018ArmLimited