On Tue, Jun 13, 2023 at 05:48:44PM -0400, Steven Rostedt wrote: > On Wed, 7 Jun 2023 09:42:30 -0700 > Jiri Olsa <olsajiri@xxxxxxxxx> wrote: > > > I can't really reliable reproduce this, but while checking the code, I wonder > > we should call rethook_free only after we call unregister_ftrace_function like > > in the patch below > > Yeah, I think you're right! > > > > > jirka > > > > > > --- > > diff --git a/kernel/trace/fprobe.c b/kernel/trace/fprobe.c > > index 18d36842faf5..0121e8c0d54e 100644 > > --- a/kernel/trace/fprobe.c > > +++ b/kernel/trace/fprobe.c > > @@ -364,19 +364,13 @@ int unregister_fprobe(struct fprobe *fp) > > fp->ops.saved_func != fprobe_kprobe_handler)) > > return -EINVAL; > > > > - /* > > - * rethook_free() starts disabling the rethook, but the rethook handlers > > - * may be running on other processors at this point. To make sure that all > > - * current running handlers are finished, call unregister_ftrace_function() > > - * after this. > > - */ > > - if (fp->rethook) > > - rethook_free(fp->rethook); > > The above only waits for RCU to finish and then starts to free rethook. > > This also means that something could be on the trampoline already and was > preempted. It could be that this code path gets preempted. Anyway, I don't > see how freeing rethook is safe before disabling all users. > > Reviewed-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> thanks, I'll send formal patch jirka > > -- Steve > > > > - > > ret = unregister_ftrace_function(&fp->ops); > > if (ret < 0) > > return ret; > > > > + if (fp->rethook) > > + rethook_free(fp->rethook); > > + > > ftrace_free_filter(&fp->ops); > > > > return ret; >
