bpf: Add schedule points in batch ops

syzbot reported various soft lockups caused by bpf batch operations. INFO: task kworker/1:1:27 blocked for more than 140 seconds. INFO: task hung in rcu_barrier Nothing prevents batch ops to process huge amount of data, we need to add schedule points in them. Note that maybe_wait_bpf_programs(map) calls from generic_map_delete_batch() can be factorized by moving the call after the loop. This will be done later in -next tree once we get this fix merged, unless there is strong opinion doing this optimization sooner. Fixes: aa2e93b ("bpf: Add generic support for update and delete batch ops") Fixes: cb4d03a ("bpf: Add generic support for lookup batch op") Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org> Reviewed-by: Stanislav Fomichev <sdf@google.com> Acked-by: Brian Vazquez <brianvv@google.com> Link: https://lore.kernel.org/bpf/20220217181902.808742-1-eric.dumazet@gmail.com

Author: edumazet

kernel/bpf/syscall.c

@@ -1355,6 +1355,7 @@ int generic_map_delete_batch(struct bpf_map *map,
 maybe_wait_bpf_programs(map);
 if (err)
 break;
+cond_resched();
 }
 if (copy_to_user(&uattr->batch.count, &cp, sizeof(cp)))
 err = -EFAULT;
@@ -1412,6 +1413,7 @@ int generic_map_update_batch(struct bpf_map *map,
 
 if (err)
 break;
+cond_resched();
 }
 
 if (copy_to_user(&uattr->batch.count, &cp, sizeof(cp)))
@@ -1509,6 +1511,7 @@ int generic_map_lookup_batch(struct bpf_map *map,
 swap(prev_key, key);
 retry = MAP_LOOKUP_RETRIES;
 cp++;
+cond_resched();
 }
 
 if (err == -EFAULT)