Re: objtool warnings for kernel/trace/trace_selftest_dynamic.o

From: Peter Zijlstra
Date: Mon Dec 17 2018 - 17:35:44 EST

On Mon, Dec 17, 2018 at 12:55:35PM -0800, Andi Kleen wrote:
> On Mon, Dec 17, 2018 at 08:29:38PM +0100, Peter Zijlstra wrote:
> > When/if we get the LTO trainwreck sorted -- which very much includes
> > getting that memory-order-consume fixed -- we can revisit all that.
> What do you mean? I'm not aware of any LTO problems with memory-order-consume?

The compiler is basically allowed to break RCU (and anything else that
depends on read-read dependencies). LTO makes it _far_ more likely this

We need guarantees (and possible switches) from the compiler folks that
this will not happen before I'll retract my NAK from any LTO enabling.