bpf: add schedule points in percpu arrays management

[ upstream commit 32fff23 ] syszbot managed to trigger RCU detected stalls in bpf_array_free_percpu() It takes time to allocate a huge percpu map, but even more time to free it. Since we run in process context, use cond_resched() to yield cpu if needed. Fixes: a10423b ("bpf: introduce BPF_MAP_TYPE_PERCPU_ARRAY map") Signed-off-by: Eric Dumazet <[email protected]> Reported-by: syzbot <[email protected]> Signed-off-by: Daniel Borkmann <[email protected]> Signed-off-by: Greg Kroah-Hartman <[email protected]>
intel · Mar 11, 2018 · e1760b3 · e1760b3
1 parent 03549a3
commit e1760b3
Showing 1 changed file with 4 additions and 1 deletion.
diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
@@ -23,8 +23,10 @@ static void bpf_array_free_percpu(struct bpf_array *array)
 {
 	int i;
 
-	for (i = 0; i < array->map.max_entries; i++)
+	for (i = 0; i < array->map.max_entries; i++) {
 		free_percpu(array->pptrs[i]);
+		cond_resched();
+	}
 }
 
 static int bpf_array_alloc_percpu(struct bpf_array *array)
@@ -40,6 +42,7 @@ static int bpf_array_alloc_percpu(struct bpf_array *array)
 			return -ENOMEM;
 		}
 		array->pptrs[i] = ptr;
+		cond_resched();
 	}
 
 	return 0;