libcryfs/test/implementations/caching/cache/CacheTest_RaceCondition.cpp

106 lines
3.5 KiB
C++

#include "testutils/CacheTest.h"
#include <chrono>
#include <thread>
#include <memory>
#include <future>
#include <messmer/cpp-utils/lock/ConditionBarrier.h>
using namespace std::chrono_literals;
using namespace blockstore::caching;
using std::string;
using cpputils::ConditionBarrier;
using std::unique_ptr;
using std::make_unique;
using std::future;
// Regression tests for a race condition.
// An element could be in the process of being thrown out of the cache and while the destructor is running, another
// thread calls pop() for the element and gets none returned. But since the destructor isn't finished yet, the data from
// the cache element also isn't completely written back yet and an application loading it runs into a race condition.
class ObjectWithLongDestructor {
public:
ObjectWithLongDestructor(ConditionBarrier *onDestructorStarted, bool *destructorFinished)
: _onDestructorStarted(onDestructorStarted), _destructorFinished(destructorFinished) {}
~ObjectWithLongDestructor() {
_onDestructorStarted->release();
std::this_thread::sleep_for(1s);
*_destructorFinished = true;
}
private:
ConditionBarrier *_onDestructorStarted;
bool *_destructorFinished;
};
class CacheTest_RaceCondition: public ::testing::Test {
public:
CacheTest_RaceCondition(): cache(), destructorStarted(), destructorFinished(false) {}
Cache<int, unique_ptr<ObjectWithLongDestructor>> cache;
ConditionBarrier destructorStarted;
bool destructorFinished;
int pushObjectWithLongDestructor() {
cache.push(2, make_unique<ObjectWithLongDestructor>(&destructorStarted, &destructorFinished));
return 2;
}
int pushDummyObject() {
cache.push(3, nullptr);
return 3;
}
future<void> causeCacheOverflowInOtherThread() {
//Add maximum+1 element in another thread (this causes the cache to flush the first element in another thread)
return std::async(std::launch::async, [this] {
for(unsigned int i = 0; i < cache.MAX_ENTRIES+1; ++i) {
cache.push(cache.MAX_ENTRIES+i, nullptr);
}
});
}
void EXPECT_POP_BLOCKS_UNTIL_DESTRUCTOR_FINISHED(int key) {
EXPECT_FALSE(destructorFinished);
cache.pop(key);
EXPECT_TRUE(destructorFinished);
}
void EXPECT_POP_DOESNT_BLOCK_UNTIL_DESTRUCTOR_FINISHED(int key) {
EXPECT_FALSE(destructorFinished);
cache.pop(key);
EXPECT_FALSE(destructorFinished);
}
};
TEST_F(CacheTest_RaceCondition, PopBlocksWhileRequestedElementIsThrownOut_ByAge) {
auto id = pushObjectWithLongDestructor();
destructorStarted.wait();
EXPECT_POP_BLOCKS_UNTIL_DESTRUCTOR_FINISHED(id);
}
TEST_F(CacheTest_RaceCondition, PopDoesntBlockWhileOtherElementIsThrownOut_ByAge) {
pushObjectWithLongDestructor();
auto id = pushDummyObject();
destructorStarted.wait();
EXPECT_POP_DOESNT_BLOCK_UNTIL_DESTRUCTOR_FINISHED(id);
}
TEST_F(CacheTest_RaceCondition, PopBlocksWhileRequestedElementIsThrownOut_ByPush) {
auto id = pushObjectWithLongDestructor();
auto future = causeCacheOverflowInOtherThread();
destructorStarted.wait();
EXPECT_POP_BLOCKS_UNTIL_DESTRUCTOR_FINISHED(id);
}
TEST_F(CacheTest_RaceCondition, PopDoesntBlockWhileOtherElementIsThrownOut_ByPush) {
pushObjectWithLongDestructor();
auto id = pushDummyObject();
auto future = causeCacheOverflowInOtherThread();
destructorStarted.wait();
EXPECT_POP_DOESNT_BLOCK_UNTIL_DESTRUCTOR_FINISHED(id);
}