An image processing apparatus and a method for controlling an image processing apparatus are disclosed. The method includes: primarily processing a first thread from among a plurality of threads for a preset process; generating and storing a first error correction code for data recorded in a stack area of a random access memory (RAM) corresponding to the first thread when a primary process terminates; processing a second thread which is different from the first thread from among the plurality of threads; determining whether the data of the stack area is valid on the basis of the stored first error correction code at a point of time when the process for the second thread terminates and a secondary process for the first thread begins; and secondarily processing the first thread by restoring the data having an error in the stack area in response to a determination that the data of the stack area is invalid.