From: Thomas Gleixner > Sent: 11 December 2020 21:11 > > On Fri, Dec 11 2020 at 14:19, David Laight wrote: > > From: Thomas Gleixner > >> You can't catch that. If this really becomes an issue you need a > >> sequence counter around it. > > > > Or just two copies of the high word. > > Provided the accesses are sequenced: > > writer: > > load high:low > > add small_value,high:low > > store high > > store low > > store high_copy > > reader: > > load high_copy > > load low > > load high > > if (high != high_copy) > > low = 0; > > And low = 0 is solving what? You need to loop back and retry until it's > consistent and then it's nothing else than an open coded sequence count. If it is a counter or timestamp then the high:0 value happened some time between when you started trying to read the value and when you finished trying to read it. As such it is a perfectly reasonable return value. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
