Swift Concurrencyとレースコンディション

After iOSDC Japan 2024
2024/8/26

Transcript

1. :VLJ
   :BTPTIJNB
   !ZBTP@TBO
   
    4XJGU
   $PODVSSFODZͱ
   ϨʔείϯσΟγϣϯ "GUFS
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   +BQBO
   
2. ඇಉظॲཧͰى͖Δ໰୊ w σʔλڝ߹
   w ϨʔείϯσΟγϣϯ ؒҧͬͨίʔυΛॻ͍ͯ΋େ఍໰୊ͳ͘ಈ͍ͯ͠·͏
3. 4XJGU
   $PODVSSFODZͰ͸ʁ w 4XJGU
   $PODVSSFODZ͕ίϯύΠϧ࣌ʹอূ͢Δͷ͸σʔλڝ߹·Ͱ
   w ϨʔείϯσΟγϣϯͷ໰୊͸ɺ
   ҎલͱมΘΒ࣮ͣ૷ऀ͕ؾΛ͚ͭΔඞཁ͕͋Δ
4. 4XJGU
   $PODVSSFODZͷ࢓૊Έ w "DUPS
   SFFOUSBODZ
   ʢ"DUPSͷ࠶ೖՄೳੑʣ
   w $PPQFSBUJWF
   5ISFBE
   1PPM
   ʢڠௐతεϨουϓʔϧʣ
5. nonisolated func asyncMethod(_ value: Int) async -> Int { ... } ... Task { @MainActor in let value = makeValue() let result = await asyncMethod(value) print("result : \(result)") } ॲཧ͕ܧଓ࣮ͯ͠ߦ͞ΕΔ୯Ґ ᶃ ᶄ ᶅ ᶃϝΠϯ ᶄ#( ᶅϝΠϯ 4VTQFOUJPO
   1PJOU εϨου $POUJOVBUJPO ϝΠϯ
6. nonisolated func asyncMethod(_ value: Int) async -> Int { ... } ... Task { @MainActor in let value = makeValue() let result = await asyncMethod(value) print("result : \(result)") } ॲཧ͕ܧଓ࣮ͯ͠ߦ͞ΕΔ୯Ґ ᶃ ᶄ ᶅ ᶃϝΠϯ ᶄ ᶅϝΠϯ 4VTQFOUJPO
   1PJOU εϨου $POUJOVBUJPO ᶄ ᶄ
7. $PPQFSBUJWF
   5ISFBE
   1PPM ڠௐతεϨουϓʔϧ εϨου εϨου ࣮ߦ଴ͪ "DUPS
   ᶃ "DUPS
   ᶄ /PO
   *TPMBUFE Task { @MainActor in let value = makeValue() let result = await asyncMethod(value) return "fetched : " + result } Task { } 5BTLͷ࣮ߦ
8. nonisolated func method() { ᶃ Task.detached { ᶄ } Task.detached { ᶅ } ᶆ } ࣮ߦ͞ΕΔॱ൪ w ᶄɺᶅɺᶆ͸ฒྻͰ࣮ߦ͞ ΕΔ શͯ/PO
   *TPMBUFEͷ৔߹ ᶃ ᶆ ᶄ
   ᶅ
   εϨου
9. nonisolated func method() { ᶃ Task.detached { ᶄ } Task.detached { ᶅ } ᶆ } ࣮ߦ͞ΕΔॱ൪ w ᶄɺᶅɺᶆ͸ฒྻͰ࣮ߦ͞ ΕΔ
   w ᶆͷޙʹᶄɺᶅ͕ಉ͡εϨ ουͷՄೳੑ΋ͳ͘͸ͳ͍ શͯ/PO
   *TPMBUFEͷ৔߹ ᶃ ᶆ ᶄ
   ᶅ
   εϨου ᶄ
   ᶅ
   
10. @MyActor func method() { ᶃ Task { @MyActor in ᶄ } Task { @MyActor in ᶅ } ᶆ } w ·ͣᶃɺᶆ͕࣮ߦ͞ΕΔ
    w ᶄɺᶅ͸
    ฒྻʹ͸࣮ߦ͞Εͳ͍͕
    ͲͪΒ͔Β
    ࣮ߦ͞ΕΔ͔͸Θ͔Βͳ͍ ࣮ߦ͞ΕΔॱ൪ ಉ͡"DUPSͷ৔߹ εϨου ᶃ ᶆ ᶄ
    ᶅ
    ᶄ
    ᶅ
    ʁ
    
11. ໰୊ͷ͋ΔίʔυΛվળ͢Δ
12. ໰୊ͷ͋Δίʔυྫ λοϓͨ͠਺ͷϩάΛૹΔ w λοϓ͢ΔͨͼʹϩʔΧϧʹอ͍࣋ͯ͠Δ਺Λ૿΍͢
    w ఆظతʹ਺Λαʔόʔʹૹ৴͢Δ
    w ૹ৴ͨ͠ΒϩʔΧϧͷ਺ΛϦηοτ͢Δ
13. ໰୊ͷ͋Δίʔυྫ actor Counter { var count: Int = 0 func increment() { count += 1 } func reset() { count = 0 } } class CountLogger { private let counter = Counter() func increment() async { await counter.increment() } // ఆظతʹؒΛ͓͍ͯݺ͹ΕΔ૝ఆ func post() async { let count = await counter.count await postCountLog(count) await counter.reset() } }
14. class CountLogger { func increment() async { ... } ... func post() async { let count = await counter.count await postCountLog(count) await counter.reset() } } w DPVOUऔಘ͔ͯ͠ΒSFTFU͢Δ·ͰͷؒʹJODSFNFOU ͕ݺ͹ΕΔͱ
    ͦͷ૿Ճ෼͸QPTU͞ΕͣʹSFTFU͞ΕΔ
15. class CountLogger { func increment() async { ... } ... func post() async { let count = await counter.count await counter.reset() await postCountLog(count) } } w DPVOUऔಘޙʹ͙͢SFTFUͯ͠΋ɺ
    4VTQFOUJPO
    1PJOUͰJODSFNFOU͕ݺ͹ΕΔՄೳੑ͕͋Δ
16. actor CountLogger { func increment() async { ... } ... func post() async { let count = await counter.count await counter.reset() await postCountLog(count) } } w BDUPSʹͯ͠΋4VTQFOUJPO
    1PJOU͕ೖΔ͜ͱ͸มΘΒͳ͍
17. վળͨ͠ίʔυ actor Counter { private var count: Int = 0 func increment() { count += 1 } func pull() -> Int { let count = self.count self.count = 0 return count } } actor CountLogger { private let counter = Counter() func increment() async { await counter.increment() } // ఆظతʹؒΛ͓͍ͯݺ͹ΕΔ૝ఆ func post() async { let count = await counter.pull() await postCountLog(count) } }
18. actor Counter { private var count: Int = 0 ... func pull() -> Int { let count = self.count self.count = 0 return count } } w DPVOUͷऔಘͱϦηοτΛBDUPSͷϝιουͭͰߦ͏͜ͱͰ
    4VTQFOUJPO
    1PJOU͕ೖΔ͜ͱͳ͘ͳΔ
19. αϯϓϧͷ࢓༷มߋ λοϓͨ͠਺ͷϩάΛૹΓ߹ܭΛදࣔ w λοϓ͢ΔͨͼʹϩʔΧϧʹอ͍࣋ͯ͠Δ਺Λ૿΍͢
    w ఆظతʹ਺Λαʔόʔʹૹ৴͢Δ
    w ૹ৴ͨ͠ΒϩʔΧϧͷ਺ΛϦηοτ͢Δ
    w ૹ৴࣌ʹαʔόʔ͔Β߹ܭΛฦ͠දࣔ͢Δ /FX
20. func post() async -> Int { let count = await counter.pull() let total = await postCountLog(count) return total } w ಉ࣌ʹݺ͹ΕΔͱɺޙ͔ΒݺΜͩํ͕ઌʹऴΘΔՄೳੑ͕͋Δ
    w BDUPS͕ಉ͡Ͱ΋ؔ܎ͳ͍ func post() async -> Int { let count = await counter.pull() let total = await postCountLog(count) return total } ઌʹݺΜͩॲཧ ޙ͔ΒݺΜͩॲཧ
21. w ݺͼग़͢λΠϛϯά͕ॏෳ͢Δͱ໰୊͕ى͖ΔՄೳੑ͕͋Δ Task { let total = await logger.post() print("total : \(total)") } ͱΓ͋͑ͣ5BTL ❓
22. 5JNFSͰ5BTLΛ܁Γฦ࣮͠ߦ w QPTUͷॲཧ͕5JNFSͷJOUFSWBMΛ௒͑Δͱɺ
    QPTUͷॲཧ͕ॏෳ͢ΔՄೳੑ͕͋Δ Timer.scheduledTimer(withTimeInterval: 10, repeats: true) { _ in Task { let total = await logger.post() print("total : \(total)") } } ❌
23. w
    5BTLͷதͰϧʔϓ͢Ε͹ɺQPTUͷॲཧ͸ॏෳ͠ͳ͍ Task { while true { await logger.post() print("total : \(total)") try await Task.sleep(for: .seconds(10)) } } 5BTLͰ܁Γฦ࣮͠ߦ
24. αϯϓϧͷ࢓༷มߋ λοϓͨ͠਺ͷϩάΛૹΓ߹ܭΛදࣔ w λοϓ͢ΔͨͼʹϩʔΧϧʹอ͍࣋ͯ͠Δ਺Λ૿΍͢
    w ఆظతʹ਺Λαʔόʔʹૹ৴͢Δ
    w ૹ৴ͨ͠ΒϩʔΧϧͷ਺ΛϦηοτ͢Δ
    w ૹ৴࣌ʹαʔόʔ͔Β߹ܭΛฦ͠දࣔ͢Δ
    w ࣗ༝ͳλΠϛϯάͰ਺Λαʔόʔʹૹ৴͢Δ /FX
25. var isProcessing: Bool = false func post() { Task { guard !isProcessing else { return } isProcessing = true let total = await logger.post() print("total : \(total)”) isProcessing = false } } ˞
    "DUPS͸ಉ͡૝ఆ ඇಉظॲཧͷॏෳΛεΩοϓ
26. w ௚઀࣮ߦͤͣɺผ5BTLͰඇಉظॲཧ͕௚ྻʹ࣮ߦ͞ΕΔΑ͏ʹ͢Δ
    w ͨͩ͠ɺݺͼग़͠ଆ͕࣮ࡍͷඇಉظॲཧͷ׬ྃΛ଴ͭ͜ͱ͸Ͱ͖ͳ͍ let channel: AsyncChannel<Void> Task { for await _ in channel { let total = await logger.post() print("total : \(total)") } } Task { await channel.send(()) } "TZOD$IBOOFMΛ࢖͏
27. ·ͱΊ 4XJGU
    $PODVSSFODZͱϨʔείϯσΟγϣϯ w 4XJGU
    $PODVSSFOUZ͸ϨʔείϯσΟγϣϯΛ๷͍Ͱ͘ΕΔ΋ͷͰ͸ͳ͍
    w Ή͠Ζޮ཰Λ༏ઌͯ͠໰୊Λى͜͠΍͍͢࢓૊Έʹͳ͍ͬͯΔ
    w "DUPS
    SFFOUSBODZ
    w ಉ͡BDUPSಉ࢜ͷॲཧͰ΋ɺBXBJUͰڬΈࠐ·ΕΔՄೳੑ͕͋Δ
    w $PPQFSBUJWF
    5ISFBE
    1PPM
    w εϨουͰ࣮ߦ͞ΕΔॱ൪͸ɺ࣮ߦ։࢝͠Α͏ͱͨ͠ॱ൪ͱ͸ݶΒͳ͍
28. ·ͱΊ ϨʔείϯσΟγϣϯ΁ͷରԠ w ہॴతʹ͸ҰͭͷBDUPSͷதͰBTZODؔ਺Λ࢖Θͣʹ
    Ͳ͏ݺ͹Εͯ΋ෆ੔߹͕ى͖ͳ͍ঢ়ଶΛ࡞Δ
    w BTZODؔ਺Λ૊Έ߹Θͤͳ͍ͱ͍͚ͳ͚Ε͹ɺ
    ΫϦςΟΧϧηΫγϣϯ͕ಉ࣌ʹ࣮ߦ͞Εͳ͍Α͏ʹߟྀ࣮ͯ͠૷͢Δ
29. ࢀߟ w 88%$
    w .FFU
    BTZODBXBJU
    JO
    4XJGU
    w 1SPUFDU
    NVUBCMF
    TUBUF
    XJUI
    4XJGU
    BDUPST
    w 4XJGU
    DPODVSSFODZ
    #FIJOE
    UIF
    TDFOFT