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Priority inversion avoidance in Actor Runtime #41362

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Merged
merged 4 commits into from
Feb 17, 2022
Merged

Priority inversion avoidance in Actor Runtime #41362

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4c736b0
Create the notion of an ActiveActorStatus which captures the atomic
rokhinip Feb 10, 2022
b318f65
Track the identity of the task draining the actor in the
rokhinip Feb 13, 2022
ac4fab8
Priority escalation support when actors run into contention
rokhinip Feb 13, 2022
a3e3c3f
Update the Reflection headers to deal with the new layout changes in the
rokhinip Feb 16, 2022
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10 changes: 7 additions & 3 deletions include/swift/Reflection/ReflectionContext.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1504,21 +1504,25 @@ class ReflectionContext

std::pair<llvm::Optional<std::string>, ActorInfo>
actorInfo(StoredPointer ActorPtr) {
using DefaultActorImpl = DefaultActorImpl<Runtime>;
if (supportsPriorityEscalation) {
return {std::string("Failure reading actor with escalation support"), {}};
}

using DefaultActorImpl = DefaultActorImpl<Runtime, ActiveActorStatusWithoutEscalation<Runtime>>;

auto ActorObj = readObj<DefaultActorImpl>(ActorPtr);
if (!ActorObj)
return {std::string("failure reading actor"), {}};

ActorInfo Info{};
Info.Flags = ActorObj->Flags;
Info.Flags = ActorObj->Status.Flags[0];

// Status is the low 3 bits of Flags. Status of 0 is Idle. Don't read
// FirstJob when idle.
auto Status = Info.Flags & 0x7;
if (Status != 0) {
// This is a JobRef which stores flags in the low bits.
Info.FirstJob = ActorObj->FirstJob & ~StoredPointer(0x3);
Info.FirstJob = ActorObj->Status.FirstJob & ~StoredPointer(0x3);
}
return {llvm::None, Info};
}
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18 changes: 15 additions & 3 deletions include/swift/Reflection/RuntimeInternals.h
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Expand Up @@ -96,7 +96,7 @@ struct StackAllocator {
template <typename Runtime>
struct ActiveTaskStatusWithEscalation {
uint32_t Flags;
uint32_t DrainLock[(sizeof(typename Runtime::StoredPointer) == 8) ? 1 : 2];
uint32_t ExecutionLock[(sizeof(typename Runtime::StoredPointer) == 8) ? 1 : 2];
typename Runtime::StoredPointer Record;
};

Expand Down Expand Up @@ -150,10 +150,22 @@ struct FutureAsyncContextPrefix {
};

template <typename Runtime>
struct ActiveActorStatusWithEscalation {
uint32_t Flags;
uint32_t DrainLock[(sizeof(typename Runtime::StoredPointer) == 8) ? 1 : 2];
typename Runtime::StoredPointer FirstJob;
};

template <typename Runtime>
struct ActiveActorStatusWithoutEscalation {
uint32_t Flags[sizeof(typename Runtime::StoredPointer) == 8 ? 2 : 1];
typename Runtime::StoredPointer FirstJob;
};

template <typename Runtime, typename ActiveActorStatus>
struct DefaultActorImpl {
HeapObject<Runtime> HeapObject;
typename Runtime::StoredPointer FirstJob;
typename Runtime::StoredSize Flags;
ActiveActorStatus Status;
};

template <typename Runtime>
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