[tip:x86/urgent] sched/core, x86: Make struct thread_info arch specific again

From: tip-bot for Heiko Carstens
Date: Fri Oct 21 2016 - 01:52:21 EST

Commit-ID: c8061485a0d7569a865a3cc3c63347b0f42b3765
Gitweb: http://git.kernel.org/tip/c8061485a0d7569a865a3cc3c63347b0f42b3765
Author: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
AuthorDate: Wed, 19 Oct 2016 19:28:11 +0100
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 20 Oct 2016 13:27:47 +0200

sched/core, x86: Make struct thread_info arch specific again

The following 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 CONFIG_THREAD_INFO_IN_TASK_STRUCT=y is

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>
Signed-off-by: Mark Rutland <mark.rutland@xxxxxxx>
Acked-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Andy Lutomirski <luto@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: keescook@xxxxxxxxxxxx
Cc: linux-arch@xxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1476901693-8492-2-git-send-email-mark.rutland@xxxxxxx
Signed-off-by: Ingo Molnar <mingo@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 2aaca53..ad6f5eb0 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 45f004e..2873baf 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)