[PATCH 5.4 09/18] idr test suite: Take RCU read lock in idr_find_test_1

[Greg Kroah-Hartman]

From: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>

[ Upstream commit 703586410da69eb40062e64d413ca33bd735917a ]

When run on a single CPU, this test would frequently access already-freed
memory.  Due to timing, this bug never showed up on multi-CPU tests.

Reported-by: Chris von Recklinghausen <crecklin@xxxxxxxxxx>
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 tools/testing/radix-tree/idr-test.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/tools/testing/radix-tree/idr-test.c b/tools/testing/radix-tree/idr-test.c
index 44ceff95a9b3..4a9b451b7ba0 100644
--- a/tools/testing/radix-tree/idr-test.c
+++ b/tools/testing/radix-tree/idr-test.c
@@ -306,11 +306,15 @@ void idr_find_test_1(int anchor_id, int throbber_id)
 	BUG_ON(idr_alloc(&find_idr, xa_mk_value(anchor_id), anchor_id,
 				anchor_id + 1, GFP_KERNEL) != anchor_id);
 
+	rcu_read_lock();
 	do {
 		int id = 0;
 		void *entry = idr_get_next(&find_idr, &id);
+		rcu_read_unlock();
 		BUG_ON(entry != xa_mk_value(id));
+		rcu_read_lock();
 	} while (time(NULL) < start + 11);
+	rcu_read_unlock();
 
 	pthread_join(throbber, NULL);
 
-- 
2.30.2