[PATCH] bpf: Call cond_resched() to avoid soft lockup in trie_free()

[Matt Fleming <matt@readmodwrite.com>]

From: Matt Fleming <mfleming@cloudflare.com>

Calls to kfree() in trie_free() can be expensive for KASAN-enabled
kernels. This can cause soft lockup warnings when traversing large maps,

  watchdog: BUG: soft lockup - CPU#41 stuck for 76s! [kworker/u518:14:1158211]

Avoid an unbounded loop and periodically check whether we should reschedule.

Signed-off-by: Matt Fleming <mfleming@cloudflare.com>
---
 kernel/bpf/lpm_trie.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/kernel/bpf/lpm_trie.c b/kernel/bpf/lpm_trie.c
index be66d7e520e0..a35619cd99f6 100644
--- a/kernel/bpf/lpm_trie.c
+++ b/kernel/bpf/lpm_trie.c
@@ -646,6 +646,8 @@ static void trie_free(struct bpf_map *map)
 			RCU_INIT_POINTER(*slot, NULL);
 			break;
 		}
+
+		cond_resched();
 	}
 
 out:
-- 
2.34.1