On Tue, May 16, 2017 at 05:04:32PM +0100, David Howells wrote: > Guenter Roeck <li...@roeck-us.net> wrote: > > > Turns out not here because ____cacheline_aligned_in_smp includes > > __page_aligned_data which also declares the section, at least on x86. > > If there's any sort of section specification, that should suffice, I think. > The problem might come that jiffies and jiffies_64 don't coincide at the same > address because FRV is BE not LE. > > It ought to be possible to make jiffies 64-bit on FRV since it has double-word > instructions that can load/store aligned 64-bit values atomically to/from a > register pair. That might require some compiler magic, though. I'll have to > try and work out if that's possible. > I tried:
diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h index 36872fbb815d..26d0655c4422 100644 --- a/include/linux/jiffies.h +++ b/include/linux/jiffies.h @@ -64,13 +64,15 @@ extern int register_refined_jiffies(long clock_tick_rate); /* TICK_USEC is the time between ticks in usec assuming fake USER_HZ */ #define TICK_USEC ((1000000UL + USER_HZ/2) / USER_HZ) +#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 __cacheline_aligned_in_smp jiffies_64; -extern unsigned long volatile __cacheline_aligned_in_smp jiffies; +extern u64 __cacheline_aligned_in_smp __jiffy_data jiffies_64; +extern unsigned long volatile __cacheline_aligned_in_smp __jiffy_data jiffies; This is what I get when building defconfig: CC arch/x86/kernel/asm-offsets.s In file included from ./include/linux/ktime.h:25:0, from ./include/linux/rcupdate.h:46, from ./include/linux/srcu.h:33, from ./include/linux/notifier.h:15, from ./include/linux/memory_hotplug.h:6, from ./include/linux/mmzone.h:757, from ./include/linux/gfp.h:5, from ./include/linux/slab.h:14, from ./include/linux/crypto.h:24, from arch/x86/kernel/asm-offsets.c:8: ./include/linux/jiffies.h:74:52: error: section of ‘jiffies_64’ conflicts with previous declaration extern u64 __cacheline_aligned_in_smp __jiffy_data jiffies_64; ^ ./include/linux/jiffies.h:75:71: error: section of ‘jiffies’ conflicts with previous declaration extern unsigned long volatile __cacheline_aligned_in_smp __jiffy_data jiffies; ^ Kbuild:56: recipe for target 'arch/x86/kernel/asm-offsets.s' failed make[1]: *** [arch/x86/kernel/asm-offsets.s] Error 1 Makefile:1061: recipe for target 'prepare0' failed make: *** [prepare0] Error 2 Guenter