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[tip:x86/asm] thread_info: Use unsigned long for flags

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Commit-ID:  907241dccb4ce5d9413cf3c030b32b0cfc184914
Gitweb:     http://git.kernel.org/tip/907241dccb4ce5d9413cf3c030b32b0cfc184914
Author:     Mark Rutland <mark.rutland@arm.com>
AuthorDate: Fri, 23 Sep 2016 18:24:07 +0100
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Sat, 24 Sep 2016 09:35:06 +0200

thread_info: Use unsigned long for flags

The generic THREAD_INFO_IN_TASK definition of thread_info::flags is a
u32, matching x86 prior to the introduction of THREAD_INFO_IN_TASK.

However, common helpers like test_ti_thread_flag() implicitly assume
that thread_info::flags has at least the size and alignment of unsigned
long, and relying on padding and alignment provided by other elements of
task_struct is somewhat fragile. Additionally, some architectures use
more that 32 bits for thread_info::flags, and others may need to in
future.

With THREAD_INFO_IN_TASK, task struct follows thread_info with a long
field, and thus we no longer save any space as we did back in commit:

  affa219b60a11b32 ("x86: change thread_info's flag field back to 32 bits")

Given all this, it makes more sense for the generic thread_info::flags
to be an unsigned long.

In fact given <linux/thread_info.h> contains/uses the helpers mentioned
above, BE arches *must* use unsigned long (or something of the same size)
today, or they wouldn't work.

Make it so.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/1474651447-30447-1-git-send-email-mark.rutland@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 include/linux/thread_info.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index e2d0fd8..45f004e 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -15,7 +15,7 @@ struct compat_timespec;
 
 #ifdef CONFIG_THREAD_INFO_IN_TASK
 struct thread_info {
-	u32			flags;		/* low level flags */
+	unsigned long		flags;		/* low level flags */
 };
 
 #define INIT_THREAD_INFO(tsk)			\

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Thread

[PATCH] thread_info: use unsigned long for flags Mark Rutland <mark.rutland@arm.com> - 2016-09-23 19:30 +0200
  Re: [PATCH] thread_info: use unsigned long for flags Andy Lutomirski <luto@amacapital.net> - 2016-09-23 20:10 +0200
    Re: [PATCH] thread_info: use unsigned long for flags Mark Rutland <mark.rutland@arm.com> - 2016-09-24 01:50 +0200
  [tip:x86/asm] thread_info: Use unsigned long for flags tip-bot for Mark Rutland <tipbot@zytor.com> - 2016-09-24 18:40 +0200

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