linux-kernel - Re: [PATCH] frv: Declare jiffies to be located in the .data section

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Message-ID: <20170516222857.GA9588@roeck-us.net>
Date:   Tue, 16 May 2017 15:28:57 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Matthias Kaehlcke <mka@...omium.org>
Cc:     David Howells <dhowells@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] frv: Declare jiffies to be located in the .data section

On Tue, May 16, 2017 at 03:13:33PM -0700, Matthias Kaehlcke wrote:
> Commit 7c30f352c852 ("jiffies.h: declare jiffies and jiffies_64 with
> ____cacheline_aligned_in_smp") removed a section specification from the
> jiffies declaration that caused conflicts on some platforms. Unfortunately
> this change broke the build for frv:
> 
> kernel/built-in.o: In function `__do_softirq':
> (.text+0x6460): relocation truncated to fit: R_FRV_GPREL12 against symbol
>     `jiffies' defined in *ABS* section in .tmp_vmlinux1
> kernel/built-in.o: In function `__do_softirq':
> (.text+0x6574): relocation truncated to fit: R_FRV_GPREL12 against symbol
>     `jiffies' defined in *ABS* section in .tmp_vmlinux1
> kernel/built-in.o: In function `pwq_activate_delayed_work':
> workqueue.c:(.text+0x15b9c): relocation truncated to fit: R_FRV_GPREL12 against
>     symbol `jiffies' defined in *ABS* section in .tmp_vmlinux1
> ...
> 
> Add __jiffy_arch_data to the declaration of jiffies and use it on frv to
> include the section specification. For all other platforms __jiffy_arch_data
> (currently) has no effect.
> 
> Fixes: 7c30f352c852 ("jiffies.h: declare jiffies and jiffies_64 with
> ____cacheline_aligned_in_smp")
> Signed-off-by: Matthias Kaehlcke <mka@...omium.org>

Tested-by: Guenter Roeck <linux@...ck-us.net>

[frv:defconfig and x86_64:defconfig]

> ---
>  arch/frv/include/asm/timex.h | 6 ++++++
>  include/linux/jiffies.h      | 6 +++++-
>  2 files changed, 11 insertions(+), 1 deletion(-)
> 
> diff --git a/arch/frv/include/asm/timex.h b/arch/frv/include/asm/timex.h
> index a89bddefdacf..139093fab326 100644
> --- a/arch/frv/include/asm/timex.h
> +++ b/arch/frv/include/asm/timex.h
> @@ -16,5 +16,11 @@ static inline cycles_t get_cycles(void)
>  #define vxtime_lock()		do {} while (0)
>  #define vxtime_unlock()		do {} while (0)
>  
> +/* This attribute is used in include/linux/jiffies.h alongside with
> + * __cacheline_aligned_in_smp. It is assumed that __cacheline_aligned_in_smp
> + * for frv does not contain another section specification.
> + */
> +#define __jiffy_arch_data	__attribute__((__section__(".data")))
> +
>  #endif
>  
> diff --git a/include/linux/jiffies.h b/include/linux/jiffies.h
> index 36872fbb815d..734377ad42e9 100644
> --- a/include/linux/jiffies.h
> +++ b/include/linux/jiffies.h
> @@ -64,13 +64,17 @@ 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)
>  
> +#ifndef __jiffy_arch_data
> +#define __jiffy_arch_data
> +#endif
> +
>  /*
>   * 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 unsigned long volatile __cacheline_aligned_in_smp __jiffy_arch_data jiffies;
>  
>  #if (BITS_PER_LONG < 64)
>  u64 get_jiffies_64(void);
> -- 
> 2.13.0.303.g4ebf302169-goog
>