On Fri, Aug 25, 2017 at 11:49:47AM -0400, Steven Rostedt wrote:
> On Fri, 25 Aug 2017 12:31:13 +0200
> Thomas Gleixner <t...@linutronix.de> wrote:
>
> > The error and the spurious interrupt are really rare events and not at all
> > so performance sensitive that two NOP5s can not be tolerated when tracing
> > is disabled.
>
> Just a note. I'm sure if we disassembled it, it may be a little more
> work done than just two NOPs, as parameter passing to the tracepoints
> sometimes leak out of the static jump block. It's moot on this patch,
> but other irqs with fast paths may need to be looked at.
Is that something we can fix with the trace macros?
They have a general shape of:
#define trace_foo(args...)
if (static_branch_unlikely(&foo_enabled)) {
__trace_foo(args...);
}
Right? And I suppose I see why the compiler would want to sometimes lift
stuff out of the branch block, but we'd really like it not to do that.
Would putting a barrier() in front of __trace_foo() help?
