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[SYCL] avoid lock and wait in KernelProgramCache::getOrBuild #20780

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Merged
sergey-semenov merged 1 commit into from
Nov 28, 2025
Merged

[SYCL] avoid lock and wait in KernelProgramCache::getOrBuild #20780

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27 changes: 12 additions & 15 deletions sycl/source/detail/kernel_program_cache.hpp
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Original file line number Diff line number Diff line change
Expand Up @@ -90,15 +90,10 @@ class KernelProgramCache {
/// A mutex to be employed along with MBuildCV.
std::mutex MBuildResultMutex;

BuildState
waitUntilTransition(BuildState From = BuildState::BS_InProgress) {
BuildState To;
BuildState waitUntilTransition() {
std::unique_lock<std::mutex> Lock(MBuildResultMutex);
MBuildCV.wait(Lock, [&] {
To = State;
return State != From;
});
return To;
MBuildCV.wait(Lock, [&] { return State != BuildState::BS_InProgress; });
return State.load();
}

void updateAndNotify(BuildState DesiredState) {
Expand Down Expand Up @@ -729,29 +724,31 @@ class KernelProgramCache {
auto /* std::shared_ptr<BuildResult> */
getOrBuild(GetCachedBuildFT &&GetCachedBuild, BuildFT &&Build,
EvictFT &&EvictFunc = nullptr) {
using BuildState = KernelProgramCache::BuildState;
constexpr size_t MaxAttempts = 2;
for (size_t AttemptCounter = 0;; ++AttemptCounter) {
auto /* std::pair<std::shared_ptr<BuildResult>, bool> */ Res =
GetCachedBuild();
auto &BuildResult = Res.first;
assert(BuildResult != nullptr);
BuildState Expected = BuildState::BS_Initial;
BuildState Desired = BuildState::BS_InProgress;
if (!BuildResult->State.compare_exchange_strong(Expected, Desired)) {
BuildState CurrentState = BuildState::BS_Initial; // initial is expected
if (!BuildResult->State.compare_exchange_strong(
CurrentState, BuildState::BS_InProgress)) {
// no insertion took place, thus some other thread has already inserted
// smth in the cache
BuildState NewState = BuildResult->waitUntilTransition();

if (CurrentState == BuildState::BS_InProgress) {
CurrentState = BuildResult->waitUntilTransition();
}

// Build succeeded.
if (NewState == BuildState::BS_Done) {
if (CurrentState == BuildState::BS_Done) {
if constexpr (!std::is_same_v<EvictFT, void *>)
EvictFunc(BuildResult->Val, /*IsBuilt=*/false);
return BuildResult;
}

// Build failed, or this is the last attempt.
if (NewState == BuildState::BS_Failed ||
if (CurrentState == BuildState::BS_Failed ||
AttemptCounter + 1 == MaxAttempts) {
if (BuildResult->Error.isFilledIn())
throw detail::set_ur_error(
Expand Down
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