diff --git a/kernel/console.c b/kernel/console.c
index b8fa1de..d6eb209 100644
--- a/kernel/console.c
+++ b/kernel/console.c
@@ -89,7 +89,7 @@ consoleread(int user_dst, uint64 dst, int n)
     // wait until interrupt handler has put some
     // input into cons.buffer.
     while(cons.r == cons.w){
-      if(__sync_add_and_fetch(&(myproc()->killed), 0)){
+      if(killed(myproc())){
         release(&cons.lock);
         return -1;
       }
diff --git a/kernel/defs.h b/kernel/defs.h
index 62b9292..7181d4d 100644
--- a/kernel/defs.h
+++ b/kernel/defs.h
@@ -90,6 +90,7 @@ void            proc_mapstacks(pagetable_t);
 pagetable_t     proc_pagetable(struct proc *);
 void            proc_freepagetable(pagetable_t, uint64);
 int             kill(int);
+int             killed(struct proc*);
 struct cpu*     mycpu(void);
 struct cpu*     getmycpu(void);
 struct proc*    myproc();
diff --git a/kernel/pipe.c b/kernel/pipe.c
index e438d7e..f6b501a 100644
--- a/kernel/pipe.c
+++ b/kernel/pipe.c
@@ -81,7 +81,7 @@ pipewrite(struct pipe *pi, uint64 addr, int n)
 
   acquire(&pi->lock);
   while(i < n){
-    if(pi->readopen == 0 || __sync_add_and_fetch(&pr->killed,0)){
+    if(pi->readopen == 0 || killed(pr)){
       release(&pi->lock);
       return -1;
     }
@@ -111,7 +111,7 @@ piperead(struct pipe *pi, uint64 addr, int n)
 
   acquire(&pi->lock);
   while(pi->nread == pi->nwrite && pi->writeopen){  //DOC: pipe-empty
-    if(__sync_add_and_fetch(&pr->killed,0)){
+    if(killed(pr)){
       release(&pi->lock);
       return -1;
     }
diff --git a/kernel/proc.c b/kernel/proc.c
index 221f0f8..24680b6 100644
--- a/kernel/proc.c
+++ b/kernel/proc.c
@@ -422,7 +422,7 @@ wait(uint64 addr)
     }
 
     // No point waiting if we don't have any children.
-    if(!havekids || __sync_add_and_fetch(&p->killed, 0)){
+    if(!havekids || killed(p)){
       release(&wait_lock);
       return -1;
     }
@@ -601,6 +601,12 @@ kill(int pid)
   return -1;
 }
 
+int
+killed(struct proc *p)
+{
+  return __sync_add_and_fetch(&p->killed, 0);
+}
+
 // Copy to either a user address, or kernel address,
 // depending on usr_dst.
 // Returns 0 on success, -1 on error.
diff --git a/kernel/sysproc.c b/kernel/sysproc.c
index 61b715b..99a36a7 100644
--- a/kernel/sysproc.c
+++ b/kernel/sysproc.c
@@ -63,7 +63,7 @@ sys_sleep(void)
   acquire(&tickslock);
   ticks0 = ticks;
   while(ticks - ticks0 < n){
-    if(__sync_add_and_fetch(&(myproc()->killed), 0)){
+    if(killed(myproc())){
       release(&tickslock);
       return -1;
     }
diff --git a/kernel/trap.c b/kernel/trap.c
index b879f01..f895aea 100644
--- a/kernel/trap.c
+++ b/kernel/trap.c
@@ -53,7 +53,7 @@ usertrap(void)
   if(r_scause() == 8){
     // system call
 
-    if(__sync_add_and_fetch(&p->killed, 0))
+    if(killed(p))
       exit(-1);
 
     // sepc points to the ecall instruction,
@@ -73,7 +73,7 @@ usertrap(void)
     __sync_bool_compare_and_swap(&p->killed, 0, 1);
   }
 
-  if(__sync_add_and_fetch(&p->killed, 0))
+  if(killed(p))
     exit(-1);
 
   // give up the CPU if this is a timer interrupt.