Peter Zijlstra <pet...@infradead.org> writes: > On Fri, Aug 04, 2017 at 10:05:55AM +0800, Huang, Ying wrote: >> "Huang, Ying" <ying.hu...@intel.com> writes: >> > Peter Zijlstra <pet...@infradead.org> writes: > >> >> +struct __call_single_data { >> >> struct llist_node llist; >> >> smp_call_func_t func; >> >> void *info; >> >> unsigned int flags; >> >> }; >> >> >> >> +typedef struct __call_single_data call_single_data_t >> >> + __aligned(sizeof(struct __call_single_data)); >> >> + >> > >> > Another requirement of the alignment is that it should be the power of >> > 2. Otherwise, for example, if someone adds a field to struct, so that >> > the size becomes 40 on x86_64. The alignment should be 64 instead of >> > 40. >> >> Thanks Aaron, he reminded me that there is a roundup_pow_of_two(). So >> the typedef could be, >> >> typedef struct __call_single_data call_single_data_t >> __aligned(roundup_pow_of_two(sizeof(struct __call_single_data)); >> > > Yes, that would take away the requirement to play padding games with the > struct. Then again, maybe its a good thing to have to be explicit about > it. > > If you see: > > struct __call_single_data { > struct llist_node llist; > smp_call_func_t func; > void *info > int flags; > void *extra_field; > > unsigned long __padding[3]; /* make align work */ > }; > > that makes it very clear what is going on. In any case, we can delay > this part because the current structure is a power-of-2 for both ILP32 > and LP64. So only the person growing this will have to deal with it ;-)
Yes. That looks good. So you will prepare the final patch? Or you hope me to do that? Best Regards, Huang, Ying