Index: sys/x86/x86/mca.c
===================================================================
--- sys/x86/x86/mca.c
+++ sys/x86/x86/mca.c
@@ -560,16 +560,29 @@
 mca_fill_freelist(void)
 {
 	struct mca_internal *rec;
-	int desired;
+	int desired_high, desired_low;
 
 	/*
 	 * Ensure we have at least one record for each bank and one
-	 * record per CPU.
+	 * record per CPU. Also, free excess entries which have crept onto
+	 * our list. Do the frees first in case a concurrent thread begins
+	 * using the free list entries while this thread is still working.
 	 */
-	desired = imax(mp_ncpus, mca_banks);
+	desired_low = imax(mp_ncpus, mca_banks);
+	desired_high = imax(mp_ncpus, mca_banks) * 2;
 	mtx_lock_spin(&mca_lock);
-	while (mca_freecount < desired) {
+	while (mca_freecount > desired_high) {
+		rec = STAILQ_FIRST(&mca_freelist);
+		KASSERT(rec != NULL, ("mca_freecount is %d, but list is empty",
+		    mca_freecount));
+		STAILQ_REMOVE_HEAD(&mca_freelist, link);
+		mca_freecount--;
 		mtx_unlock_spin(&mca_lock);
+		free(rec, M_MCA);
+		mtx_lock_spin(&mca_lock);
+	}
+	while (mca_freecount < desired_low) {
+		mtx_unlock_spin(&mca_lock);
 		rec = malloc(sizeof(*rec), M_MCA, M_WAITOK);
 		mtx_lock_spin(&mca_lock);
 		STAILQ_INSERT_TAIL(&mca_freelist, rec, link);
@@ -821,13 +834,17 @@
 	thread_unlock(td);
 	if (count != 0) {
 		mtx_lock_spin(&mca_lock);
-		STAILQ_FOREACH(mca, &mca_records, link) {
+		while ((mca = STAILQ_FIRST(&mca_records)) != NULL) {
 			if (!mca->logged) {
 				mca->logged = 1;
 				mca_log(&mca->rec);
 			}
+			STAILQ_REMOVE_HEAD(&mca_records, link);
+			STAILQ_INSERT_TAIL(&mca_freelist, rec, link);
+			mca_freecount++;
 		}
 		mtx_unlock_spin(&mca_lock);
+		mca_fill_freelist();
 	}
 }
 
@@ -1334,13 +1351,18 @@
 	/* If we found anything, log them to the console. */
 	if (count != 0) {
 		mtx_lock_spin(&mca_lock);
-		STAILQ_FOREACH(mca, &mca_records, link) {
+		while ((mca = STAILQ_FIRST(&mca_records)) != NULL) {
 			if (!mca->logged) {
 				mca->logged = 1;
 				mca_log(&mca->rec);
 			}
+			STAILQ_REMOVE_HEAD(&mca_records, link);
+			STAILQ_INSERT_TAIL(&mca_freelist, rec, link);
+			mca_freecount++;
 		}
 		mtx_unlock_spin(&mca_lock);
+		if (!cold)
+			taskqueue_enqueue(mca_tq, &mca_refill_task);
 	}
 }
 #endif