On Thu, 3 Sep 2020 10:39:54 +0900 Masami Hiramatsu <mhiramat@xxxxxxxxxx> wrote: > OK, I've confirmed that the lockdep warns on kretprobe from INT3 > with your fix. Of course make it lockless then warning is gone. > But even without the lockless patch, this warning can be false-positive > because we prohibit nested kprobe call, right? > > If the kprobe user handler uses a spinlock, the spinlock is used > only in that handler (and in the context between kprobe_busy_begin/end), > it will be safe since the spinlock is not nested. > But if the spinlock is shared with other context, it will be dangerous > because it can be interrupted by NMI (including INT3). This also applied > to the function which is called from kprobe user handlers, thus user > has to take care of it. Sorry, for noticing this point, I Cc'd to systemtap. Is systemtap taking care of spinlock too? Thank you, -- Masami Hiramatsu <mhiramat@xxxxxxxxxx>
