[Linux-kernel-mentees] [PATCH 2/2] events: callchain: Use RCU API to access RCU pointer

Amol Grover frextrite at gmail.com
Wed Jan 29 16:08:13 UTC 2020


callchain_cpus_entries is annotated as an RCU pointer.
Hence rcu_dereference_protected or similar RCU API is
required to dereference the pointer.

This fixes the following sparse warning
kernel/events/callchain.c:65:17: warning: incorrect type in assignment

Signed-off-by: Amol Grover <frextrite at gmail.com>
---
 kernel/events/callchain.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index f91e1f41d25d..a672d02a1b3a 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -62,7 +62,8 @@ static void release_callchain_buffers(void)
 {
 	struct callchain_cpus_entries *entries;
 
-	entries = callchain_cpus_entries;
+	entries = rcu_dereference_protected(callchain_cpus_entries,
+					    lockdep_is_held(&callchain_mutex));
 	RCU_INIT_POINTER(callchain_cpus_entries, NULL);
 	call_rcu(&entries->rcu_head, release_callchain_buffers_rcu);
 }
-- 
2.24.1



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