locking

I have a class that is accessed from multiple threads. Both of its getter and setter functions are guarded with locks. Are the locks for the getter functions really needed? If so, why? class foo { public: void setCount (int count) { boost::lock_guard<boost::mutex> lg(mutex_); count_ = count; } int count () { boost::lock_guard<boost::mutex> lg(mutex_); // mutex needed? return count_; } private: boost::mutex mutex_; int count_; }; The only way you can get around having the lock is if you can convince yourself that the system will transfer the guarded variable atomicly in all cases. If you can't

C# doesn't allow locking on a null value. I suppose I could check whether the value is null or not before I lock it, but because I haven't locked it another thread could come along and make the value null! How can I avoid this race condition? Chris Shain Lock on a value that is never null, e.g. Object _lockOnMe = new Object(); Object _iMightBeNull; public void DoSomeKungFu() { if (_iMightBeNull == null) { lock (_lockOnMe) { if (_iMightBeNull == null) { _iMightBeNull = ... whatever ...; } } } } Also be careful to avoid this interesting race condition with double-checked locking: Memory Model

I have two threads, a producer thread that places objects into a generic List collection and a consumer thread that pulls those objects out of the same generic List. I've got the reads and writes to the collection properly synchronized using the lock keyword, and everything is working fine. What I want to know is if it is ok to access the Count property without first locking the collection. JaredPar refers to the Count property in his blog as a decision procedure that can lead to race conditions, like this: if (list.Count > 0) { return list[0]; } If the list has one item and that item is

UPDATE: I eliminated Hibernate from the problem. I completely reworked description of problem to simplify it as much as possible. I have master table with noop trigger and detail table with two relations between master and detail table: create table detail ( id bigint not null, code varchar(255) not null, primary key (id) ); create table master ( id bigint not null, name varchar(255), detail_id bigint, -- "preferred" detail is one-to-one relation primary key (id), unique (detail_id), foreign key (detail_id) references detail(id) ); create table detail_candidate ( -- "candidate" details = many

i want to lock the phone when i click the lock button.anybody please help with simple code.i tried with part of code from API_Demos but it shows some error. You can lock the Android's screen programmatically using the LockScreen class like so: KeyguardManager mgr = (KeyguardManager)getSystemService(Activity.KEYGUARD_SERVICE); KeyguardLock lock = mgr.newKeyguardLock(KEYGUARD_SERVICE); lock.reenableKeyguard(); Take a look at the LockScreen class here . The code: KeyguardManager mgr = (KeyguardManager)getSystemService(Activity.KEYGUARD_SERVICE); KeyguardLock lock = mgr.newKeyguardLock(KEYGUARD