[PATCH 1/3] sched/core,x86: make struct thread_info arch specific again

From: Heiko Carstens
Date: Thu Oct 13 2016 - 09:02:50 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.

Signed-off-by: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
arch/x86/include/asm/thread_info.h | 9 +++++++++
include/linux/thread_info.h | 11 -----------
2 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/thread_info.h b/arch/x86/include/asm/thread_info.h
index 2aaca53c0974..ad6f5eb07a95 100644
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -52,6 +52,15 @@ struct task_struct;
#include <asm/cpufeature.h>
#include <linux/atomic.h>

+struct thread_info {
+ unsigned long flags; /* low level flags */
+#define INIT_THREAD_INFO(tsk) \
+{ \
+ .flags = 0, \
#define init_stack (init_thread_union.stack)

#else /* !__ASSEMBLY__ */
diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 45f004e9cc59..2873baf5372a 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -14,17 +14,6 @@ struct timespec;
struct compat_timespec;

-struct thread_info {
- unsigned long flags; /* low level flags */
-#define INIT_THREAD_INFO(tsk) \
-{ \
- .flags = 0, \
#define current_thread_info() ((struct thread_info *)current)