diff --git a/tests/TESTS b/tests/TESTS
index 72f11589c8..1b03efa517 100644
--- a/tests/TESTS
+++ b/tests/TESTS
@@ -18,6 +18,7 @@ opr/time
 opr/uuid
 ptserver/pt_util
 ptserver/pts-man
+rx/atomic
 rx/event
 rx/perf
 volser/vos-man
diff --git a/tests/rx/.gitignore b/tests/rx/.gitignore
index 6389919e21..230b5820df 100644
--- a/tests/rx/.gitignore
+++ b/tests/rx/.gitignore
@@ -1 +1,2 @@
+/atomic-t
 /event-t
diff --git a/tests/rx/Makefile.in b/tests/rx/Makefile.in
index 5af2d171b5..fe172e4693 100644
--- a/tests/rx/Makefile.in
+++ b/tests/rx/Makefile.in
@@ -10,10 +10,13 @@ MODULE_CFLAGS = -I$(TOP_OBJDIR)
 LIBS = $(abs_top_builddir)/tests/common/libafstest_common.la \
        $(abs_top_builddir)/src/rx/liboafs_rx.la
 
-BINS = event-t
+BINS = atomic-t event-t
 
 all: $(BINS)
 
+atomic-t: atomic-t.o $(LIBS)
+	$(LT_LDRULE_static) atomic-t.o $(LIBS) $(LIB_roken) $(XLIBS)
+
 event-t: event-t.o $(LIBS)
 	$(LT_LDRULE_static) event-t.o $(LIBS) $(LIB_roken) $(XLIBS)
 install:
diff --git a/tests/rx/atomic-t.c b/tests/rx/atomic-t.c
new file mode 100644
index 0000000000..b909e671c0
--- /dev/null
+++ b/tests/rx/atomic-t.c
@@ -0,0 +1,196 @@
+/*
+ * Copyright (c) 2022 Sine Nomine Associates. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include <afsconfig.h>
+#include <afs/param.h>
+
+#include <roken.h>
+#include <pthread.h>
+
+#include <tests/tap/basic.h>
+
+#include <afs/opr.h>
+#include <rx/rx_atomic.h>
+
+struct thread_args {
+    rx_atomic_t atom;
+    int min_val;
+    int max_val;
+};
+
+/* This runs various atomic ops using the starting value of 'val', and results
+ * in setting various values in the range [val-20,val+20]. */
+static void
+test_simple(int val)
+{
+    rx_atomic_t atom = RX_ATOMIC_INIT(val);
+
+    diag("init val %d", val);
+
+    is_int(val, rx_atomic_read(&atom), "rx_atomic_read -> %d", val);
+
+    val += 5;
+    rx_atomic_set(&atom, val);
+    is_int(val, rx_atomic_read(&atom), "rx_atomic_set -> %d", val);
+
+    val++;
+    rx_atomic_inc(&atom);
+    is_int(val, rx_atomic_read(&atom), "rx_atomic_inc -> %d", val);
+
+    val++;
+    is_int(val, rx_atomic_inc_and_read(&atom), "rx_atomic_inc_and_read -> %d", val);
+
+    val += 3;
+    rx_atomic_add(&atom, 3);
+    is_int(val, rx_atomic_read(&atom), "rx_atomic_add -> %d", val);
+
+    val += 10;
+    is_int(val, rx_atomic_add_and_read(&atom, 10), "rx_atomic_add_and_read -> %d", val);
+
+    val--;
+    rx_atomic_dec(&atom);
+    is_int(val, rx_atomic_read(&atom), "rx_atomic_dec -> %d", val);
+
+    val--;
+    is_int(val, rx_atomic_dec_and_read(&atom), "rx_atomic_dec_and_read -> %d", val);
+
+    val -= 3;
+    rx_atomic_sub(&atom, 3);
+    is_int(val, rx_atomic_read(&atom), "rx_atomic_sub -> %d", val);
+
+    /* Get back to 20 below the initial value. */
+    val -= 35;
+    rx_atomic_sub(&atom, 35);
+    is_int(val, rx_atomic_read(&atom), "rx_atomic_sub -> %d", val);
+}
+
+static void *
+atom_thread(void *rock)
+{
+#define I_REPS 1000
+#define J_REPS 1000
+
+    struct thread_args *args = rock;
+    rx_atomic_t *atom = &args->atom;
+    int i, j;
+    int val;
+    const char *last_op;
+
+    for (i = 0; i < I_REPS; i++) {
+	last_op = "rx_atomic_inc/dec";
+	for (j = 0; j < J_REPS; j++) {
+	    rx_atomic_inc(atom);
+	    rx_atomic_dec(atom);
+	}
+
+	val = rx_atomic_read(atom);
+	if (val < args->min_val || val > args->max_val) {
+	    goto fail;
+	}
+
+	for (j = 0; j < J_REPS; j++) {
+	    val = rx_atomic_inc_and_read(atom);
+	    if (val < args->min_val || val > args->max_val) {
+		last_op = "rx_atomic_inc_and_read";
+		goto fail;
+	    }
+
+	    val = rx_atomic_dec_and_read(atom);
+	    if (val < args->min_val || val > args->max_val) {
+		last_op = "rx_atomic_dec_and_read";
+		goto fail;
+	    }
+	}
+
+	last_op = "rx_atomic/add/sub/add_and_read";
+	for (j = 0; j < J_REPS; j++) {
+	    rx_atomic_add(atom, 2);
+	    rx_atomic_sub(atom, 4);
+	    val = rx_atomic_add_and_read(atom, 2);
+	    if (val < args->min_val || val > args->max_val) {
+		goto fail;
+	    }
+	}
+    }
+
+    return rock;
+
+ fail:
+    printf("# bad value after %s: %d (min %d, max %d)\n",
+	   last_op, val, args->min_val, args->max_val);
+    return NULL;
+}
+
+static void
+test_threads(int val)
+{
+#define N_THREADS 10
+    pthread_t tid[N_THREADS];
+    struct thread_args args;
+    int thread_i;
+
+    memset(&args, 0, sizeof(args));
+    args.min_val = val - N_THREADS * 2;
+    args.max_val = val + N_THREADS * 2;
+
+    diag("threaded init val %d", val);
+
+    rx_atomic_set(&args.atom, val);
+
+    for (thread_i = 0; thread_i < N_THREADS; thread_i++) {
+	opr_Verify(pthread_create(&tid[thread_i], NULL, atom_thread, &args) == 0);
+    }
+
+    for (thread_i = 0; thread_i < N_THREADS; thread_i++) {
+	void *ret;
+	opr_Verify(pthread_join(tid[thread_i], &ret) == 0);
+
+	ok(ret != NULL, "atom thread %d/%d", thread_i, N_THREADS - 1);
+    }
+
+    is_int(val, rx_atomic_read(&args.atom), "final atomic value");
+}
+
+int
+main(void)
+{
+    plan(61);
+
+    test_simple(0);
+
+    /* Pick a couple of values that will cause us to cross from positive to
+     * negative, and negative to positive, for at least one operation. */
+    test_simple(14);
+    test_simple(-14);
+
+    /* Pick a couple of large values somewhat close to positive/negative 2^31,
+     * but not close enough that we overflow. */
+    test_simple(2147483600);
+    test_simple(-2147483600);
+
+    test_threads(0);
+
+    return 0;
+}
+