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

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The following commit:

  c65eacbe29 ("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
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@de.ibm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: keescook@chromium.org
Cc: linux-arch@vger.kernel.org
Link: http://lkml.kernel.org/r/1476901693-8492-2-git-send-email-mark.rutland@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Heiko Carstens 2016-10-19 19:28:11 +01:00 committed by Ingo Molnar
parent ed1e7db33c
commit c8061485a0
2 changed files with 9 additions and 11 deletions
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9
arch/x86/include/asm/thread_info.h
View File

@ -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__ */

11
include/linux/thread_info.h
View File

@ -13,17 +13,6 @@
struct timespec;
struct compat_timespec;
#ifdef CONFIG_THREAD_INFO_IN_TASK
struct thread_info {
unsigned long flags; /* low level flags */
};
#define INIT_THREAD_INFO(tsk) \
{ \
.flags = 0, \
}
#endif
#ifdef CONFIG_THREAD_INFO_IN_TASK
#define current_thread_info() ((struct thread_info *)current)
#endif