[PATCH 0/3] THREAD_INFO_IN_TASK_STRUCT vs generic preemption code

From: Heiko Carstens
Date: Thu Oct 13 2016 - 08:42:54 EST

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.

The above is actually the same as the description of the first
patch. The second patch is a simple compile fix and the third one the
s390 conversion to THREAD_INFO_IN_TASK_STRUCT.

Heiko Carstens (3):
sched/core,x86: make struct thread_info arch specific again
sched/preempt: include asm/current.h
s390: move thread_info into task_struct

arch/s390/Kconfig | 1 +
arch/s390/include/asm/lowcore.h | 2 +-
arch/s390/include/asm/thread_info.h | 11 --------
arch/s390/kernel/asm-offsets.c | 17 +++++--------
arch/s390/kernel/entry.S | 51 ++++++++++++++++++-------------------
arch/s390/kernel/head64.S | 5 ++--
arch/s390/kernel/setup.c | 3 +--
arch/s390/kernel/smp.c | 1 -
arch/x86/include/asm/thread_info.h | 9 +++++++
include/asm-generic/preempt.h | 1 +
include/linux/thread_info.h | 11 --------
11 files changed, 47 insertions(+), 65 deletions(-)