linux-kernel - [PATCH] thread_info: include <current.h> for THREAD_INFO_IN_TASK (WAS: [PATCH 2/3] sched/preempt: include asm/current.h)

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Date:   Fri, 14 Oct 2016 11:42:25 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Heiko Carstens <heiko.carstens@...ibm.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        "H . Peter Anvin" <hpa@...or.com>, linux-arch@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Mark Rutland <mark.rutland@....com>
Subject: [PATCH] thread_info: include <current.h> for THREAD_INFO_IN_TASK (WAS: [PATCH 2/3] sched/preempt: include asm/current.h)

When CONFIG_THREAD_INFO_IN_TASK is selected, the current_thread_info()
macro relies on current having been defined prior to its use. However,
not all users of current_thread_info() include <asm/current.h>, and thus
current is not guaranteed to be defined.

When CONFIG_THREAD_INFO_IN_TASK is not selected, it's possible that
get_current() / current are based upon current_thread_info(), and
<asm/current.h> includes <asm/thread_info.h>. Thus always including
<asm/current.h> would result in circular dependences on some platforms.

To ensure both cases work, this patch includes <asm/current.h>, but only
when CONFIG_THREAD_INFO_IN_TASK is selected.

Signed-off-by: Mark Rutland <mark.rutland@....com>
---
 include/linux/thread_info.h | 1 +
 1 file changed, 1 insertion(+)

As discussed, it would be great if this could go in along with the patch to
make thread_info arch-specific again, to make merging the arch-specific parts
easier (for arm64 and s390).

Mark.

diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h
index 45f004e..521f84b 100644
--- a/include/linux/thread_info.h
+++ b/include/linux/thread_info.h
@@ -25,6 +25,7 @@ struct thread_info {
 #endif

 #ifdef CONFIG_THREAD_INFO_IN_TASK
+#include <asm/current.h>
 #define current_thread_info() ((struct thread_info *)current)
 #endif

-- 
1.9.1