Threadsafe variable

In my kernel i have a variable

shared float total;

I only have a single block and that block contains 200 threads.

Now if the variable is updated by all the 200 threads at the same time, will the variable be thread safe?

how do we deal with condition like this when all the threads on a block updates a single variable at the same time??

thank you

Atomic operations on shared memory locations are supported on Compute 1.2 and above.