Hi Elad, Thanks very much for your time and clarification! Best Regards Nan Xiao On Mon, Nov 11, 2024 at 8:05 PM Elad Lahav <e2lahav@xxxxxxxxx> wrote: > > > Machine-sized means smaller than or equal to sizeof(long). > > > > Take a look at the implementation of WRITE_ONCE or READ_ONCE of linux. > > That is not necessarily true. What sizes and alignments are guaranteed > to be atomic for access (i.e., writing a value to a memory location > results in everyone seeing either the old value or the new value, > never a mix) is defined by the hardware architecture, and need not > align with the C definition of long. You can use the C11 > ATOMIC_*_LOCK_FREE() to determine if a type is atomic. > > As Akira points out, the term "atomic" is overloaded, and can cause > much confusion. A type being atomic for read or write access does not > imply atomic read-modify-write. > > --Elad
