On Mon, 22 May 2023 10:07:42 +0800 Ze Gao <zegao2021@xxxxxxxxx> wrote: > Oops, I missed that. Thanks for pointing that out, which I thought is > conditional use of rcu_is_watching before. > > One last point, I think we should double check on this > "fentry does not filter with !rcu_is_watching" > as quoted from Yonghong and argue whether it needs > the same check for fentry as well. rcu_is_watching() comment says; * if the current CPU is not in its idle loop or is in an interrupt or * NMI handler, return true. Thus it returns *fault* if the current CPU is in the idle loop and not any interrupt(including NMI) context. This means if any tracable function is called from idle loop, it can be !rcu_is_watching(). I meant, this is 'context' based check, thus fentry can not filter out that some commonly used functions is called from that context but it can be detected. Thank you, > > Regards, > Ze -- Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
