On Wed, Nov 13, 2024 at 03:14:09PM +0100, Uros Bizjak wrote: > > > Even without atomicity guarantee, __READ_ONCE() still prevents the > > > compiler from performing unwanted optimizations (please see the first > > > comment in include/asm-generic/rwonce.h) and unwanted reordering of > > > reads and writes when this function is inlined. This macro does cast > > > the read to volatile, but IMO it is much more readable to use > > > __READ_ONCE() than volatile qualifier. > > > > Yes it does, but please explain to me what "unwanted reordering" is > > allowed here? > > It is a static function that will be inlined by the compiler > somewhere, so "unwanted reordering" depends on where it will be > inlined. *IF* it will be called from safe code, then this limitation > for the compiler can be lifted. As long as the values are read within the spinlock the order does not matter. READ_ONCE() is not required to contain reads within spinlocks. Jason
