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fix(KeySetCache): remove a race condition

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thanks to Umut for pointing it
This commit is contained in:
rudy
2022-05-03 10:57:48 +02:00
committed by rudy-6-4
parent ab8c22c6a0
commit 8c25a97133
1 changed files with 16 additions and 18 deletions
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34
compiler/lib/ClientLib/KeySetCache.cpp
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@@ -197,18 +197,6 @@ KeySetCache::loadOrGenerateSave(ClientParameters &params, uint64_t seed_msb,
llvm::sys::path::append(folderPath, std::to_string(seed_msb) + "_" +
std::to_string(seed_lsb));
if (llvm::sys::fs::exists(folderPath)) {
auto keys = loadKeys(params, seed_msb, seed_lsb, std::string(folderPath));
if (keys.has_value()) {
return keys;
} else {
std::cerr << std::string(keys.error().mesg) << "\n";
std::cerr << "Regenerating KeySetCache entry " << std::string(folderPath)
<< "\n";
llvm::sys::fs::remove_directories(folderPath);
}
}
// Creating a lock for concurrent generation
llvm::SmallString<0> lockPath(folderPath);
lockPath.append("lock");
@@ -225,19 +213,29 @@ KeySetCache::loadOrGenerateSave(ClientParameters &params, uint64_t seed_msb,
<< std::string(lockPath) << "\": " << err.message();
}
// The first to lock will generate while the others waits
llvm::sys::fs::lockFile(FD_lock);
auto cleanUnlock = llvm::make_scope_exit([&]() {
// The lock is released when the function returns.
// => any intermediate state in the function is not visible to others.
auto unlockAtReturn = llvm::make_scope_exit([&]() {
llvm::sys::fs::unlockFile(FD_lock);
llvm::sys::fs::remove(lockPath);
});
llvm::sys::fs::lockFile(FD_lock);
if (llvm::sys::fs::exists(folderPath)) {
// Others returns here
return loadKeys(params, seed_msb, seed_lsb, std::string(folderPath));
// Once it has been generated by another process (or was alread here)
auto keys = loadKeys(params, seed_msb, seed_lsb, std::string(folderPath));
if (keys.has_value()) {
return keys;
} else {
std::cerr << std::string(keys.error().mesg) << "\n";
std::cerr << "Invalid KeySetCache entry " << std::string(folderPath)
<< "\n";
llvm::sys::fs::remove_directories(folderPath);
// Then we can continue as it didn't exist
}
}
std::cerr << "KeySetCache: miss, regenerating \n";
std::cerr << "KeySetCache: miss, regenerating\n";
OUTCOME_TRY(auto key_set, KeySet::generate(params, seed_msb, seed_lsb));
OUTCOME_TRYV(saveKeys(*key_set, folderPath));