On Wed, Oct 19, 2016 at 11:28 AM, Mark Rutland <[email protected]> wrote: > From: Heiko Carstens <[email protected]> > > commit c65eacbe290b ("sched/core: Allow putting thread_info into > task_struct") made struct thread_info a generic struct with only a > single flags member if THREAD_INFO_IN_TASK_STRUCT is selected. > > This change however seems to be quite x86 centric, since at least the > generic preemption code (asm-generic/preempt.h) assumes that struct > thread_info also has a preempt_count member, which apparently was not > true for x86. > > We could add a bit more ifdefs to solve this problem too, but it seems > to be much simpler to make struct thread_info arch specific > again. This also makes the conversion to THREAD_INFO_IN_TASK_STRUCT a > bit easier for architectures that have a couple of arch specific stuff > in their thread_info definition. > > The arch specific stuff _could_ be moved to thread_struct. However > keeping them in thread_info makes it easier: accessing thread_info > members is simple, since it is at the beginning of the task_struct, > while the thread_struct is at the end. At least on s390 the offsets > needed to access members of the thread_struct (with task_struct as > base) are too large for various asm instructions. This is not a > problem when keeping these members within thread_info.
Acked-by: Andy Lutomirski <[email protected]> Ingo, there's a (somewhat weak) argument for sending this via tip/urgent: it doesn't change generated code at all, and I think it will avoid a silly depedency or possible conflict for the next merge window, since both arm64 and s390 are going to need it. --Andy
