Index: sys/netpfil/ipfw/dn_aqm_pie.h
===================================================================
--- sys/netpfil/ipfw/dn_aqm_pie.h
+++ sys/netpfil/ipfw/dn_aqm_pie.h
@@ -97,7 +97,8 @@
 /* PIE current state */
 enum { 
 	PIE_ACTIVE = 1,
-	PIE_INMEASUREMENT = 2
+	PIE_INMEASUREMENT = 2,
+	PIE_STOP_CALLOUT = 4
 };
 
 /* 
Index: sys/netpfil/ipfw/dn_aqm_pie.c
===================================================================
--- sys/netpfil/ipfw/dn_aqm_pie.c
+++ sys/netpfil/ipfw/dn_aqm_pie.c
@@ -207,23 +205,14 @@
 	struct dn_aqm_pie_parms *pprms;
 	struct pie_status *pst = (struct pie_status *) x;
 
-	/* dealing with race condition */
-	if (callout_pending(&pst->aqm_pie_callout)) {
-		/* callout was reset */
-		mtx_unlock(&pst->lock_mtx);
-		return;
-	}
-
-	if (!callout_active(&pst->aqm_pie_callout)) {
+	if (pst->sflags & PIE_STOP_CALLOUT) {
 		/* callout was stopped */
 		mtx_unlock(&pst->lock_mtx);
 		mtx_destroy(&pst->lock_mtx);
 		free(x, M_DUMMYNET);
-		//pst->pq->aqm_status = NULL;
 		pie_desc.ref_count--;
 		return;
 	}
-	callout_deactivate(&pst->aqm_pie_callout);
 
 	pprms = pst->parms;
 	prob = pst->drop_prob;
@@ -576,7 +565,7 @@
 	
 	do { /* exit with break when error occurs*/
 		if (!pprms){
-			D("AQM_PIE is not configured");
+			DX(2, "AQM_PIE is not configured");
 			err = EINVAL;
 			break;
 		}
@@ -640,22 +629,19 @@
 		return 1;
 	}
 
+	/* Signal the callout function (calculate_drop_prob) to stop and free the
+	 * allocated memory.
+	 * We set sflag to PIE_STOP_CALLOUT and resetting callout to be executed
+	 * in the next microsecond. When the time is elapsed, calculate_drop_prob
+	 * will free the allocated memory and will not reschedule the callout.
+	 */
 	mtx_lock(&pst->lock_mtx);
+	pst->sflags  |= PIE_STOP_CALLOUT;
+	callout_reset_sbt(&pst->aqm_pie_callout,
+		SBT_1US, 0, calculate_drop_prob, pst, 0);
+	q->aqm_status = NULL;
+	mtx_unlock(&pst->lock_mtx);
 
-	/* stop callout timer */
-	if (callout_stop(&pst->aqm_pie_callout) || !(pst->sflags & PIE_ACTIVE)) {
-		mtx_unlock(&pst->lock_mtx);
-		mtx_destroy(&pst->lock_mtx);
-		free(q->aqm_status, M_DUMMYNET);
-		q->aqm_status = NULL;
-		pie_desc.ref_count--;
-		return 0;
-	} else {
-		q->aqm_status = NULL;
-		mtx_unlock(&pst->lock_mtx);
-		DX(2, "PIE callout has not been stoped from cleanup!");
-		return EBUSY;
-	}
 	return 0;
 }