On Tue, May 16, 2017 at 10:58:20AM -0700, Matthias Kaehlcke wrote: > El Tue, May 16, 2017 at 10:21:30AM -0700 Guenter Roeck ha dit: > > > On Tue, May 16, 2017 at 05:04:32PM +0100, David Howells wrote: > > > Guenter Roeck <[email protected]> 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 > > Thanks for giving it a try! > > What would work is this: > > diff --git a/arch/frv/include/asm/cache.h b/arch/frv/include/asm/cache.h > index 2797163b8f4f..25bf4e85f582 100644 > --- a/arch/frv/include/asm/cache.h > +++ b/arch/frv/include/asm/cache.h > @@ -20,4 +20,6 @@ > #define __cacheline_aligned __attribute__((aligned(L1_CACHE_BYTES))) > #define ____cacheline_aligned __attribute__((aligned(L1_CACHE_BYTES))) > > +#define __jiffies_arch_xyz __attribute__((__section__(".data"))) > + > #endif > diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h > index 36872fbb815d..8904eb52928d 100644 > --- a/include/linux/jiffies.h > +++ b/include/linux/jiffies.h > @@ -70,7 +70,7 @@ extern int register_refined_jiffies(long clock_tick_rate); > * 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 unsigned long volatile __cacheline_aligned_in_smp __jiffies_arch_xyz > jiffies; > > #if (BITS_PER_LONG < 64) > u64 get_jiffies_64(void); > > > We'd only have to find a halfway decent name for __jiffies_arch_xyz.
>From __jiffy_data: __jiffy_arch_data or __jiffies_arch_data. You'd also need #ifndef __jiffy_arch_data #define __jiffy_arch_data #endif That assumes that __cacheline_aligned_in_smp is not defined to be part of a different section for the architecture, which I guess should be acceptable here (but maybe asks for a respective comment). Guenter
