On Mon, 23 Jan 2023 21:50:12 +0100 Peter Zijlstra <pet...@infradead.org> wrote:
> All RCU disabled code should be noinstr and hence we should never get > here -- when we do, WARN about it and make sure to not actually do > tracing. > > Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> > --- > arch/x86/kernel/ftrace.c | 3 +++ > 1 file changed, 3 insertions(+) > > --- a/arch/x86/kernel/ftrace.c > +++ b/arch/x86/kernel/ftrace.c > @@ -646,6 +646,9 @@ void prepare_ftrace_return(unsigned long > if (unlikely(atomic_read(¤t->tracing_graph_pause))) > return; > > + if (WARN_ONCE(!rcu_is_watching(), "RCU not on for: %pS\n", (void *)ip)) > + return; > + Please add this to after recursion trylock below. Although WARN_ONCE() should not not have recursion issues, as function tracing can do weird things, I rather be safe than sorry, and not have the system triple boot due to some path that might get added in the future. If rcu_is_watching() is false, it will still get by the below recursion check and warn. That is, the below check should be done before this function calls any other function. > bit = ftrace_test_recursion_trylock(ip, *parent); > if (bit < 0) > return; > -- Steve _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization
