On Tue, Nov 03, 2020 at 12:58:45PM +0000, Mark Rutland wrote: > On Tue, Nov 03, 2020 at 12:17:21PM +0000, Will Deacon wrote: > > When building with LTO, there is an increased risk of the compiler > > converting an address dependency headed by a READ_ONCE() invocation > > into a control dependency and consequently allowing for harmful > > reordering by the CPU. > > > > Ensure that such transformations are harmless by overriding the generic > > READ_ONCE() definition with one that provides acquire semantics when > > building with LTO. > > > > Acked-by: Peter Zijlstra (Intel) <[email protected]> > > Signed-off-by: Will Deacon <[email protected]> > > [...] > > Could we add a note above __READ_ONCE() along the lines of the commit > message, e.g. > > /* > * With LTO a compiler might convert an address dependency headed by a > * READ_ONCE() into a control dependency, allowing for harmful > * reordering by the CPU. > * > * To prevent this, upgrade READ_OONCE() to provide acquire semantics > * when building with LTO.
It's not halloween any moooore :) But yes, I'll add something to that effect, cheers. Will
