thread-safety

问题 This question already has answers here : std::vector, thread-safety, multi-threading (3 answers) Closed 9 months ago . I have a below code that gives segmentation fault sometime? vector<int> myvector; void function1() { for(int i = 0;i<10;i++) { cout<<"writer thread:"<<i<<endl; myvector.push_back(i); } } void function2() { for(int i = 0;i<10;i++) { cout<<"reader thread:"; cout<<myvector[i]<<endl; } } int main() { thread t1(function1); thread t2(function2); t1.join(); t2.join(); } I am little

问题 I use very often RIA WCF Services and I inject the same context in several ViewModel. My problem is that as you know, the context of RIA Services, is not thread safe. So I my solution "home made" for synchronization. I use backgrounds workers, and using PostSharp, I apply my attribute [UniqueThread ("Data")] on the method and voila. Do I complicate things? Are there simpler solutions? Best regards, Vincent BOUZON 回答1: In our case we added an OnUiThread method to our BaseViewModel (which also

问题 As titled, several thread accessing one variable, and only one thread will change the variable, and all the others will just read its value. Like this: Thread 1 : while True: a += 1 Thread 2, 3, 4,... : print a In this case, only Thread 1 is changing variable a . Will any serious problems happen? I found a similar C/C++ tagged question titled "in which cases do I need to lock a variable from simultaneous access?", and it seems from the answer, that the only thing I need to worry about is that

问题 I'm maintaining a very old application, and recently I came across a 'multi thread' bug. Here, in a method, to insert a value into a db, the record is first checked that it exists or not, then if it does not exist, it is inserted into the db. createSomething(params) { .... .... if( !isPresentInDb(params) ) { ..... ..... ..... insertIntoDb(params) } ... } Here when multiple threads invoke this method, two or more threads with same params may cross the isPresentInDb check, one thread inserts

问题 In Delphi 10.1 Berlin I would like to make a TParallel.&For loop responsive. I have a parallel loop similar to the example in question TParallel.For: Store values in a TList while they are calculated in a TParallel.For loop . The loop calculates values and stores these values in a TList<Real> . I try to run the TParallel.&For in a separate thread with TTask.Run to make it responsive: type TCalculationProject=class(TObject) private Task: ITask; ... public List: TList<Real>; ... end; function

问题 I wonder, how is asynchronism implemented in AS3? Lets take the Timer class. A timer runs asynchronously and dispatches some events. Seems like it creates a new thread for himself. And how are the functions, called when timer event occurs, being thread safe? How is thread safety implemented in AS3? 回答1: AS3 now supports multi threading using "ActionScript Workers" in the latest build. You can see how it is used here in this preview... http://www.bytearray.org/?p=4423 回答2: AS3 [used to be] not

问题 Is my below method thread safe? This method is in Singleton class. private static final Map<String, PreparedStatement> holder = new ConcurrentHashMap<>(); public BoundStatement getStatement(String cql) { Session session = TestUtils.getInstance().getSession(); PreparedStatement ps = holder.get(cql); if(ps == null) { // If "ps" is already present in cache, then we don't have to synchronize and make threads wait. synchronized { ps = holder.get(cql); if (ps == null) { ps = session.prepare(cql);

问题 I'm currently reinventing the wheel of a thread pool in C++. I've eliminated almost all locks from the code, except for multiple instances of the following construct: std::atomic_size_t counter; void produce() { ++counter; } void try_consume() { if (counter != 0) { --counter; // ... } else { // ... } } So, I need a thread-safe lock-free version of this function: bool take(std::atomic_size_t& value) { if (value != 0) { --value; return true; } return false; } There is one solution that I know

问题 I am just starting to look into multi-threaded programming and thread safety. I am familiar with busy-waiting and after a bit of research I am now familiar with the theory behind spin locks, so I thought I would have a look at OSSpinLock's implementation on the Mac. It boils down to the following function (defined in objc-os.h): static inline void ARRSpinLockLock(ARRSpinLock *l) { again: /* ... Busy-waiting ... */ thread_switch(THREAD_NULL, SWITCH_OPTION_DEPRESS, 1); goto again; } (Full

问题 I'm puzzled over the result of this code: In one thread I'm writing to the ring buffer (see implementation of ring buffer here): - (void)appendToRingBuffer:(Packet *)packet { int32_t length = ((PacketAudioBuffer *)packet).totalSize; void *writePointer; bytesAvailableToWrite = [ringBuffer lengthAvailableToWriteReturningPointer:&writePointer]; memcpy(writePointer, [((PacketAudioBuffer *)packet).audioBufferData bytes], length); [ringBuffer didWriteLength:length]; //updates ring buffer head