Re: [PATCH 3/3] lockdep: Use line-buffered printk() for lockdep messages.

[Tetsuo Handa]

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.