Edge capture mode

I am trying to capture the time between falling and rising edge of a switch, the following code gets stuck on the line :

while((GPTMRIS_R & 0x04)==0){}; //Wait till captured

Any help ? 

Sorry for the messy code 

#define GPIO_PORTF_DATA_R       (*((volatile unsigned long *)0x400253FC))
#define GPIO_PORTF_DIR_R        (*((volatile unsigned long *)0x40025400))
#define GPIO_PORTF_AFSEL_R      (*((volatile unsigned long *)0x40025420))
#define GPIO_PORTF_PUR_R        (*((volatile unsigned long *)0x40025510))
#define GPIO_PORTF_PDR_R        (*((volatile unsigned long *)0x40025514))
#define GPIO_PORTF_DEN_R        (*((volatile unsigned long *)0x4002551C))
#define GPIO_PORTF_LOCK_R       (*((volatile unsigned long *)0x40025520))
#define GPIO_PORTF_CR_R         (*((volatile unsigned long *)0x40025524))
#define GPIO_PORTF_AMSEL_R      (*((volatile unsigned long *)0x40025528))
#define GPIO_PORTF_PCTL_R       (*((volatile unsigned long *)0x4002552C))
#define SYSCTL_RCGC2_R          (*((volatile unsigned long *)0x400FE108))


#define NVIC_ST_CTRL_R      (*((volatile unsigned long *)0xE000E010))
#define NVIC_ST_RELOAD_R    (*((volatile unsigned long *)0xE000E014))
#define NVIC_ST_CURRENT_R   (*((volatile unsigned long *)0xE000E018))


#define RCGCTIMER_R							(*((volatile unsigned long *)0x400FE604))
#define GPTMCTL_R								(*((volatile unsigned long *)0x4003000C))
#define GPTMCFG_R								(*((volatile unsigned long *)0x40030000))
#define GPTMTAMR_R 							(*((volatile unsigned long *)0x40030004))
	
#define GPTMICR_R								(*((volatile unsigned long *)0x40030024))
#define GPTMRIS_R								(*((volatile unsigned long *)0x4003001C))
#define GPTMTAR_R								(*((volatile unsigned long *)0x40030048))

void Timer0_Init(void);
void SysTick_Init(void);
void SysTick_Wait(unsigned long delay);
void SysTick_Wait10ms(unsigned long delay);



//   Function Prototypes
void PortF_Init(void);
void Delay(void);
void EnableInterrupts(void);


// 3. Subroutines Section

int main(void){    
 
  
  PortF_Init();         
  SysTick_Init();
	unsigned long RisingEdge;
	unsigned long FallingEdge;
	unsigned long time;
  while(1){
    
    
    
		GPTMICR_R = 0x04; 
		while((GPTMRIS_R & 0x04)==0){}; 							//Wait till captured
		RisingEdge = 	GPTMTAR_R; 		//Time of rising edge
		GPTMICR_R =4; 														//clear timer capture flag
		while((GPTMRIS_R & 4)==0){}; 							//Wait till captured
		FallingEdge = GPTMTAR_R; 		//Time of falling edge
		time = FallingEdge - RisingEdge;
		time = time * 80000000;
}
	}

void PortF_Init(void){ 
	volatile unsigned long delay;
  SYSCTL_RCGC2_R |= 0x00000020;     // 1) F clock
  delay = SYSCTL_RCGC2_R;           // delay   
  GPIO_PORTF_LOCK_R = 0x4C4F434B;   // 2) unlock PortF PF0  
  GPIO_PORTF_CR_R = 0x1F;           // allow changes to PF4-0       
  GPIO_PORTF_AMSEL_R = 0x00;        // 3) disable analog function
  GPIO_PORTF_PCTL_R = 0x00000000;   // 4) GPIO clear bit PCTL  
  GPIO_PORTF_DIR_R = 0x0E;          // 5) 
  GPIO_PORTF_AFSEL_R = 0x00;        // 6) no alternate function
  GPIO_PORTF_PUR_R = 0x11;          // enable pullup resistors on PF4,PF0       
  

	GPIO_PORTF_AFSEL_R |= 0x01;        		// 5) alternate for PF0   
	GPIO_PORTF_PCTL_R &=~0x0000000F;
	GPIO_PORTF_PCTL_R  |= 0x00000007;	
	
	GPIO_PORTF_DEN_R = 0x1F;          // 7) enable digital pins PF4-PF0   
}


void SysTick_Init(void){
  NVIC_ST_CTRL_R = 0;               // disable SysTick during setup
  NVIC_ST_CTRL_R = 0x00000005;      // enable SysTick with core clock
}
// The delay parameter is in units of the 80 MHz core clock. (12.5 ns)
void SysTick_Wait(unsigned long delay){
  NVIC_ST_RELOAD_R = 80*delay-1;  // number of counts to wait
  NVIC_ST_CURRENT_R = 0;       // any value written to CURRENT clears
  while((NVIC_ST_CTRL_R&0x00010000)==0){ // wait for count flag
  }
}
void SysTick_Wait10ms(unsigned long delay){
  unsigned long i;
  for(i=0; i<delay; i++){
    SysTick_Wait(800000);  // wait 10ms
  }
}

void Timer0_Init(void)
{
		RCGCTIMER_R |= 0x01;    	//Enable and provide a clock to 16/32-bit general-purpose timer module 0 in Run mode
		GPTMCTL_R &= ~0x01;				//Timer A is disabled
		GPTMCFG_R	 = 0x4;					//For a 16/32-bit timer, this value selects the 16-bit timer configuration
		GPTMTAMR_R 	|= 0x17;     	//Capture mode , Edge-Time mode , Capture or compare mode is enabled,  The timer counts up. When counting up, the timer starts from a
															//value of 0x00
		GPTMCTL_R |= 0x0C;				//Timer is sensetive to both edges
		GPTMCTL_R |= 0x01;				//Enable timerA
}