diff --git a/kernel/main.c b/kernel/main.c
index 24fe214..107a20c 100644
--- a/kernel/main.c
+++ b/kernel/main.c
@@ -28,8 +28,7 @@ main()
     __sync_synchronize();
     started = 1;
   } else {
-    while(started == 0)
-      ;
+    while(started == 0) {}
     __sync_synchronize();
     printf("hart %d starting\n", cpuid());
     kvminithart();  // turn on paging
diff --git a/kernel/printf.c b/kernel/printf.c
index 006da3c..16b1a94 100644
--- a/kernel/printf.c
+++ b/kernel/printf.c
@@ -123,8 +123,7 @@ panic(char *s)
   printf(s);
   printf("\n");
   panicked = 1; // freeze uart output from other CPUs
-  for(;;)
-    ;
+  for(;;) {}
 }
 
 void
diff --git a/kernel/spinlock.c b/kernel/spinlock.c
index 29d02db..c4247d6 100644
--- a/kernel/spinlock.c
+++ b/kernel/spinlock.c
@@ -60,9 +60,8 @@ acquire(struct spinlock *lk)
   if(holding(lk)) // If the lock is already held, panic.
     panic("acquire");
 
-  // See file header for details
-  while(__sync_lock_test_and_set(&lk->locked, 1) != 0)
-    ;
+  // Spin until aquired. See file header for details
+  while(__sync_lock_test_and_set(&lk->locked, 1) != 0) {}
   __sync_synchronize(); // No loads/stores after this point
 
   // Record info about lock acquisition for holding() and debugging.
diff --git a/kernel/string.c b/kernel/string.c
index cc637d3..5f3d4ac 100644
--- a/kernel/string.c
+++ b/kernel/string.c
@@ -73,8 +73,7 @@ strncpy(char *s, const char *t, int n)
   char *os;
 
   os = s;
-  while(n-- > 0 && (*s++ = *t++) != 0)
-    ;
+  while(n-- > 0 && (*s++ = *t++) != 0) {}
   while(n-- > 0)
     *s++ = 0;
   return os;
@@ -89,8 +88,7 @@ safestrcpy(char *s, const char *t, int n)
   os = s;
   if(n <= 0)
     return os;
-  while(--n > 0 && (*s++ = *t++) != 0)
-    ;
+  while(--n > 0 && (*s++ = *t++) != 0) {}
   *s = 0;
   return os;
 }
@@ -100,7 +98,6 @@ strlen(const char *s)
 {
   int n;
 
-  for(n = 0; s[n]; n++)
-    ;
+  for(n = 0; s[n]; n++) {}
   return n;
 }
diff --git a/kernel/uart.c b/kernel/uart.c
index 9409002..370472e 100644
--- a/kernel/uart.c
+++ b/kernel/uart.c
@@ -89,8 +89,7 @@ uartputc(int c)
   acquire(&uart_tx_lock);
 
   if(panicked) {
-    for(;;)
-      ;
+    for(;;) {}
   }
   while(uart_tx_w == uart_tx_r + UART_TX_BUF_SIZE) {
     // buffer is full.
@@ -113,13 +112,11 @@ uartputc_sync(int c)
   push_off();
 
   if(panicked) {
-    for(;;)
-      ;
+    for(;;) {}
   }
 
   // wait for Transmit Holding Empty to be set in LSR.
-  while((ReadReg(LSR) & LSR_TX_IDLE) == 0)
-    ;
+  while((ReadReg(LSR) & LSR_TX_IDLE) == 0) {}
   WriteReg(THR, c);
 
   pop_off();
diff --git a/user/ls.c b/user/ls.c
index 629494f..4efb969 100644
--- a/user/ls.c
+++ b/user/ls.c
@@ -10,8 +10,7 @@ fmtname(char *path)
   char       *p;
 
   // Find first character after last slash.
-  for(p = path + strlen(path); p >= path && *p != '/'; p--)
-    ;
+  for(p = path + strlen(path); p >= path && *p != '/'; p--) {}
   p++;
 
   // Return blank-padded name.
diff --git a/user/ulib.c b/user/ulib.c
index 332d1da..e7a6e95 100644
--- a/user/ulib.c
+++ b/user/ulib.c
@@ -20,8 +20,7 @@ strcpy(char *s, const char *t)
   char *os;
 
   os = s;
-  while((*s++ = *t++) != 0)
-    ;
+  while((*s++ = *t++) != 0) {}
   return os;
 }
 
@@ -38,8 +37,7 @@ strlen(const char *s)
 {
   int n;
 
-  for(n = 0; s[n]; n++)
-    ;
+  for(n = 0; s[n]; n++) {}
   return n;
 }
 
diff --git a/user/usertests.c b/user/usertests.c
index d078540..a809516 100644
--- a/user/usertests.c
+++ b/user/usertests.c
@@ -823,8 +823,7 @@ preempt(char *s)
     exit(1);
   }
   if(pid1 == 0)
-    for(;;)
-      ;
+    for(;;) {}
 
   pid2 = fork();
   if(pid2 < 0) {
@@ -832,8 +831,7 @@ preempt(char *s)
     exit(1);
   }
   if(pid2 == 0)
-    for(;;)
-      ;
+    for(;;) {}
 
   pipe(pfds);
   pid3 = fork();
@@ -846,8 +844,7 @@ preempt(char *s)
     if(write(pfds[1], "x", 1) != 1)
       printf("%s: preempt write error", s);
     close(pfds[1]);
-    for(;;)
-      ;
+    for(;;) {}
   }
 
   close(pfds[1]);