diff --git a/sys/kern/sys_timerfd.c b/sys/kern/sys_timerfd.c
--- a/sys/kern/sys_timerfd.c
+++ b/sys/kern/sys_timerfd.c
@@ -59,6 +59,8 @@
 #endif
 
 static MALLOC_DEFINE(M_TIMERFD, "timerfd", "timerfd structures");
+static struct mtx tfdlist_lock;
+MTX_SYSINIT(tfdlist_lock, &tfdlist_lock, "timerfd list locker", MTX_DEF);
 static LIST_HEAD(, timerfd) timerfd_head;
 static struct unrhdr64 tfdino_unr;
 
@@ -125,6 +127,7 @@
 	struct timespec boottime, diff;
 
 	timerfd_getboottime(&boottime);
+	mtx_lock(&tfdlist_lock);
 	LIST_FOREACH(tfd, &timerfd_head, entry) {
 		mtx_lock(&tfd->tfd_lock);
 		if (tfd->tfd_clockid != CLOCK_REALTIME ||
@@ -160,6 +163,7 @@
 		tfd->tfd_boottim = boottime;
 		mtx_unlock(&tfd->tfd_lock);
 	}
+	mtx_unlock(&tfdlist_lock);
 }
 
 static int
@@ -318,7 +322,9 @@
 	seldrain(&tfd->tfd_sel);
 	knlist_destroy(&tfd->tfd_sel.si_note);
 	mtx_destroy(&tfd->tfd_lock);
+	mtx_lock(&tfdlist_lock);
 	LIST_REMOVE(tfd, entry);
+	mtx_unlock(&tfdlist_lock);
 	free(tfd, M_TIMERFD);
 	fp->f_ops = &badfileops;
 
@@ -431,7 +437,9 @@
 	knlist_init_mtx(&tfd->tfd_sel.si_note, &tfd->tfd_lock);
 	timerfd_getboottime(&tfd->tfd_boottim);
 	getnanotime(&tfd->tfd_birthtim);
+	mtx_lock(&tfdlist_lock);
 	LIST_INSERT_HEAD(&timerfd_head, tfd, entry);
+	mtx_unlock(&tfdlist_lock);
 
 	error = falloc(td, &fp, &fd, fflags);
 	if (error != 0)