On 2018/11/06 17:38, Petr Mladek wrote: > If you would want to avoid buffering, you could set the number > of buffers to zero. Then it would always fallback to > the direct printk(). 1 lock held by swapper/1/0: #0: ( rcu_read_lock ){....} , at: trace_call_bpf+0xf8/0x640 kernel/trace/bpf_trace.c:46 is not welcomed and 1 lock held by swapper/1/0: #0: (rcu_read_lock){....}, at: trace_call_bpf+0xf8/0x640 kernel/trace/bpf_trace.c:46 is welcomed. If you want to avoid fallback to direct printk(), please allocate on-stack buffer with appropriate size. Since lockdep splat may happen when kernel stack is already tight, blindly allocating large buffer on the stack is not good.