diff --git a/share/man/man9/Makefile b/share/man/man9/Makefile
--- a/share/man/man9/Makefile
+++ b/share/man/man9/Makefile
@@ -928,7 +928,8 @@
 	cpuset.9 CPU_OR_ATOMIC.9 \
 	cpuset.9 CPU_COPY_STORE_REL.9
 MLINKS+=critical_enter.9 critical.9 \
-	critical_enter.9 critical_exit.9
+	critical_enter.9 critical_exit.9 \
+	critical_enter.9 CRITICAL_ASSERT.9
 MLINKS+=crypto_buffer.9 crypto_apply.9 \
 	crypto_buffer.9 crypto_apply_buf.9 \
 	crypto_buffer.9 crypto_buffer_contiguous_segment.9 \
diff --git a/share/man/man9/critical_enter.9 b/share/man/man9/critical_enter.9
--- a/share/man/man9/critical_enter.9
+++ b/share/man/man9/critical_enter.9
@@ -23,7 +23,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd October 5, 2005
+.Dd January 30, 2023
 .Dt CRITICAL_ENTER 9
 .Os
 .Sh NAME
@@ -37,14 +37,18 @@
 .Fn critical_enter "void"
 .Ft void
 .Fn critical_exit "void"
+.In sys/kassert.h
+.Fn CRITICAL_ASSERT "struct thread *td"
 .Sh DESCRIPTION
 These functions are used to prevent preemption in a critical region of code.
 All that is guaranteed is that the thread currently executing on a CPU will
 not be preempted.
-Specifically, a thread in a critical region will not migrate to another
-CPU while it is in a critical region.
+Specifically, a thread in a critical region will not migrate to another CPU
+while it is in a critical region, nor will the current CPU switch to a
+different thread.
 The current CPU may still trigger faults and exceptions during a critical
 section; however, these faults are usually fatal.
+The CPU might also receive and handle interrupts within a critical section.
 .Pp
 The
 .Fn critical_enter
@@ -68,6 +72,16 @@
 semaphores, or other synchronization primitives.
 One exception to this is that spin mutexes include a critical section,
 so in certain cases critical sections may be interlocked with spin mutexes.
+.Pp
+The
+.Fn CRITICAL_ASSERT
+macro verifies that the provided thread
+.Fa td
+is currently executing in a critical section.
+It is a wrapper around
+.Xr KASSERT 9 .
+.Sh SEE ALSO
+.Xr KASSERT 9
 .Sh HISTORY
 These functions were introduced in
 .Fx 5.0 .