On Mon, Jul 2, 2018 at 7:30 PM, Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> wrote: > ----- On Jul 2, 2018, at 10:18 PM, Linus Torvalds torvalds@xxxxxxxxxxxxxxxxxxxx wrote: > >> On Mon, Jul 2, 2018 at 7:01 PM Mathieu Desnoyers >> <mathieu.desnoyers@xxxxxxxxxxxx> wrote: >>> >>> One thing to consider is how we will implement the load of that pointer >>> on the kernel side. >> >> Use "get_user()". It works for 64-bit objects too, and it will be >> atomic in the 32-bit sub-parts on a 32-bit architecture. > > Is it really ? Last time we had this discussion, not all architectures > guaranteed that reading a 64-bit integer would happen in two atomic > 32-bit sub-parts. This was the main motivation for the LINUX_FIELD_u32_u64() > macro as it stands today (rather than using a union). > If you're nervous, you could do this by open-coding: #if BITS_PER_LONG == 64 get_user(...) #else get_user(...); get_user(...); #endif No need to make the header more complicated just for this. -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
