5 files changed, 84 insertions, 2 deletions

diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 1106bb6aa01e..14d51548bea6 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -784,11 +784,11 @@ void *__radix_tree_lookup(const struct radix_tree_root *root,
         while (radix_tree_is_internal_node(node)) {
                 unsigned offset;
 
-                if (node == RADIX_TREE_RETRY)
-                        goto restart;
                 parent = entry_to_node(node);
                 offset = radix_tree_descend(parent, &node, index);
                 slot = parent->slots + offset;
+                if (node == RADIX_TREE_RETRY)
+                        goto restart;
                 if (parent->shift == 0)
                         break;
         }
diff --git a/tools/testing/radix-tree/Makefile b/tools/testing/radix-tree/Makefile
index acf1afa01c5b..397d6b612502 100644
--- a/tools/testing/radix-tree/Makefile
+++ b/tools/testing/radix-tree/Makefile
@@ -7,6 +7,7 @@ LDLIBS+= -lpthread -lurcu
 TARGETS = main idr-test multiorder xarray
 CORE_OFILES := xarray.o radix-tree.o idr.o linux.o test.o find_bit.o bitmap.o
 OFILES = main.o $(CORE_OFILES) regression1.o regression2.o regression3.o \
+         regression4.o \
          tag_check.o multiorder.o idr-test.o iteration_check.o benchmark.o
 
 ifndef SHIFT
diff --git a/tools/testing/radix-tree/main.c b/tools/testing/radix-tree/main.c
index 77a44c54998f..7a22d6e3732e 100644
--- a/tools/testing/radix-tree/main.c
+++ b/tools/testing/radix-tree/main.c
@@ -308,6 +308,7 @@ int main(int argc, char **argv)
         regression1_test();
         regression2_test();
         regression3_test();
+        regression4_test();
         iteration_test(0, 10 + 90 * long_run);
         iteration_test(7, 10 + 90 * long_run);
         single_thread_tests(long_run);
diff --git a/tools/testing/radix-tree/regression.h b/tools/testing/radix-tree/regression.h
index 3c8a1584e9ee..135145af18b7 100644
--- a/tools/testing/radix-tree/regression.h
+++ b/tools/testing/radix-tree/regression.h
@@ -5,5 +5,6 @@
 void regression1_test(void);
 void regression2_test(void);
 void regression3_test(void);
+void regression4_test(void);
 
 #endif
diff --git a/tools/testing/radix-tree/regression4.c b/tools/testing/radix-tree/regression4.c
new file mode 100644
index 000000000000..cf4e5aba6b08
--- /dev/null
+++ b/tools/testing/radix-tree/regression4.c
@@ -0,0 +1,79 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/gfp.h>
+#include <linux/slab.h>
+#include <linux/radix-tree.h>
+#include <linux/rcupdate.h>
+#include <stdlib.h>
+#include <pthread.h>
+#include <stdio.h>
+#include <assert.h>
+
+#include "regression.h"
+
+static pthread_barrier_t worker_barrier;
+static int obj0, obj1;
+static RADIX_TREE(mt_tree, GFP_KERNEL);
+
+static void *reader_fn(void *arg)
+{
+        int i;
+        void *entry;
+
+        rcu_register_thread();
+        pthread_barrier_wait(&worker_barrier);
+
+        for (i = 0; i < 1000000; i++) {
+                rcu_read_lock();
+                entry = radix_tree_lookup(&mt_tree, 0);
+                rcu_read_unlock();
+                if (entry != &obj0) {
+                        printf("iteration %d bad entry = %p\n", i, entry);
+                        abort();
+                }
+        }
+
+        rcu_unregister_thread();
+
+        return NULL;
+}
+
+static void *writer_fn(void *arg)
+{
+        int i;
+
+        rcu_register_thread();
+        pthread_barrier_wait(&worker_barrier);
+
+        for (i = 0; i < 1000000; i++) {
+                radix_tree_insert(&mt_tree, 1, &obj1);
+                radix_tree_delete(&mt_tree, 1);
+        }
+
+        rcu_unregister_thread();
+
+        return NULL;
+}
+
+void regression4_test(void)
+{
+        pthread_t reader, writer;
+
+        printv(1, "regression test 4 starting\n");
+
+        radix_tree_insert(&mt_tree, 0, &obj0);
+        pthread_barrier_init(&worker_barrier, NULL, 2);
+
+        if (pthread_create(&reader, NULL, reader_fn, NULL) ||
+            pthread_create(&writer, NULL, writer_fn, NULL)) {
+                perror("pthread_create");
+                exit(1);
+        }
+
+        if (pthread_join(reader, NULL) || pthread_join(writer, NULL)) {
+                perror("pthread_join");
+                exit(1);
+        }
+
+        printv(1, "regression test 4 passed\n");
+}