Make start_timer() and stop_timer() robust against incorrect usage.

diff --git a/src/include/gpxe/retry.h b/src/include/gpxe/retry.h
index 7291db2345cc3b4281eb551529b326a452852d96..57be432e2fb4cf0459ceb40ab461f44ace98027c 100644 (file)
--- a/src/include/gpxe/retry.h
+++ b/src/include/gpxe/retry.h
@@ -15,7 +15,10 @@ struct retry_timer {
        struct list_head list;
        /** Timeout value (in ticks) */
        unsigned long timeout;
-       /** Start time (in ticks) */
+       /** Start time (in ticks)
+        *
+        * A start time of zero indicates a stopped timer.
+        */
        unsigned long start;
        /** Retry count */
        unsigned int count;

diff --git a/src/net/retry.c b/src/net/retry.c
index 0fb479522c2c653aadfc3bf94f726f31ee804777..3d9fb9899cbf292fb5f098fff38134e4aa8246ef 100644 (file)
--- a/src/net/retry.c
+++ b/src/net/retry.c
@@ -64,10 +64,11 @@ static LIST_HEAD ( timers );
  * be stopped and the timer's callback function will be called.
  */
 void start_timer ( struct retry_timer *timer ) {
+       if ( ! timer->start )
+               list_add ( &timer->list, &timers );
        timer->start = currticks();
        if ( timer->timeout < MIN_TIMEOUT )
                timer->timeout = MIN_TIMEOUT;
-       list_add ( &timer->list, &timers );
        DBG2 ( "Timer %p started\n", timer );
 }
 
@@ -82,9 +83,14 @@ void stop_timer ( struct retry_timer *timer ) {
        unsigned long old_timeout = timer->timeout;
        unsigned long runtime;
 
+       /* If timer was already stopped, do nothing */
+       if ( ! timer->start )
+               return;
+
        DBG2 ( "Timer %p stopped\n", timer );
        list_del ( &timer->list );
        runtime = currticks() - timer->start;
+       timer->start = 0;
 
        /* Update timer.  Variables are:
         *
@@ -124,6 +130,7 @@ static void timer_expired ( struct retry_timer *timer ) {
        /* Stop timer without performing RTT calculations */
        DBG2 ( "Timer %p stopped on expiry\n", timer );
        list_del ( &timer->list );
+       timer->start = 0;
        timer->count++;
 
        /* Back off the timeout value */