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Subject[PATCH 4.9 021/102] jiffies.h: declare jiffies and jiffies_64 with ____cacheline_aligned_in_smp
4.9-stable review patch.  If anyone has any objections, please let me know.


From: Matthias Kaehlcke <>

commit 7c30f352c852bae2715ad65ac4a38ca9af7d7696 upstream.

jiffies_64 is defined in kernel/time/timer.c with
____cacheline_aligned_in_smp, however this macro is not part of the
declaration of jiffies and jiffies_64 in jiffies.h.

As a result clang generates the following warning:

kernel/time/timer.c:57:26: error: section does not match previous declaration [-Werror,-Wsection]
__visible u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
include/linux/cache.h:39:36: note: expanded from macro '__cacheline_aligned_in_smp'
include/linux/cache.h:34:4: note: expanded from macro '__cacheline_aligned'
include/linux/jiffies.h:77:12: note: previous attribute is here
extern u64 __jiffy_data jiffies_64;
include/linux/jiffies.h:70:38: note: expanded from macro '__jiffy_data'

Signed-off-by: Matthias Kaehlcke <>
Cc: "Jason A . Donenfeld" <>
Cc: Grant Grundler <>
Cc: Michael Davidson <>
Cc: Greg Hackmann <>
Cc: Thomas Gleixner <>
Signed-off-by: Andrew Morton <>
Signed-off-by: Linus Torvalds <>
Cc: Nathan Chancellor <>
Signed-off-by: Greg Kroah-Hartman <>

include/linux/jiffies.h | 11 +++--------
1 file changed, 3 insertions(+), 8 deletions(-)

--- a/include/linux/jiffies.h
+++ b/include/linux/jiffies.h
@@ -1,6 +1,7 @@

+#include <linux/cache.h>
#include <linux/math64.h>
#include <linux/kernel.h>
#include <linux/types.h>
@@ -63,19 +64,13 @@ extern int register_refined_jiffies(long
/* TICK_USEC is the time between ticks in usec assuming fake USER_HZ */
#define TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ)

-/* some arch's have a small-data section that can be accessed register-relative
- * but that can only take up to, say, 4-byte variables. jiffies being part of
- * an 8-byte variable may not be correctly accessed unless we force the issue
- */
-#define __jiffy_data __attribute__((section(".data")))
* The 64-bit value is not atomic - you MUST NOT read it
* without sampling the sequence number in jiffies_lock.
* get_jiffies_64() will do this for you as appropriate.
-extern u64 __jiffy_data jiffies_64;
-extern unsigned long volatile __jiffy_data jiffies;
+extern u64 __cacheline_aligned_in_smp jiffies_64;
+extern unsigned long volatile __cacheline_aligned_in_smp jiffies;

#if (BITS_PER_LONG < 64)
u64 get_jiffies_64(void);

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