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Re: [PATCH v1 14/20] ARC: [plat-eznps] Use dedicated SMP barriers

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On Saturday 31 October 2015 06:52 PM, Noam Camus wrote:
> From: Noam Camus <noamc@ezchip.com>
>
> NPS device got 256 cores and each got 16 HW threads (SMT).
> We use EZchip dedicated ISA to trigger HW scheduler of the
> core that current HW thread belongs to.
> This scheduling makes sure that data beyond barrier is available
> to all HW threads in core and by that to all in device (4K).
>
> Signed-off-by: Noam Camus <noamc@ezchip.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> ---
>  arch/arc/include/asm/barrier.h |    8 ++++++++
>  1 files changed, 8 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arc/include/asm/barrier.h b/arch/arc/include/asm/barrier.h
> index a720998..c8229b8 100644
> --- a/arch/arc/include/asm/barrier.h
> +++ b/arch/arc/include/asm/barrier.h
> @@ -34,6 +34,12 @@
>  
>  #ifdef CONFIG_ISA_ARCOMPACT
>  
> +#ifdef CONFIG_ARC_PLAT_EZNPS
> +#include <plat/ctop.h>
> +#define mb()	asm volatile (".word %0" : : "i"(CTOP_INST_SCHD_RW) : "memory")
> +#define rmb()	asm volatile (".word %0" : : "i"(CTOP_INST_SCHD_RD) : "memory")

Do u need this even for mandatory barriers whose semantics are not related to SMP
at all ? I think you need them only for smb_*

Following is a good introduction to difference between the two !
https://community.arm.com/groups/processors/blog/2011/04/11/memory-access-ordering-part-2--barriers-and-the-linux-kernel

> +#else
> +
>  /*
>   * ARCompact based cores (ARC700) only have SYNC instruction which is super
>   * heavy weight as it flushes the pipeline as well.
> @@ -41,6 +47,8 @@
>   */
>  
>  #define mb()	asm volatile("sync\n" : : : "memory")
> +#endif /* CONFIG_ARC_PLAT_EZNPS */
> +
>  #endif
>  
>  #include <asm-generic/barrier.h>

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Thread

[PATCH v1 00/20] eznps a new ARC platform Noam Camus <noamc@ezchip.com> - 2015-10-31 14:20 +0100
  Re: [PATCH v1 02/20] clocksource: Add NPS400 timers driver Daniel Lezcano <daniel.lezcano@linaro.org> - 2015-11-01 21:50 +0100
    RE: [PATCH v1 02/20] clocksource: Add NPS400 timers driver Noam Camus <noamc@ezchip.com> - 2015-11-02 09:00 +0100
  RE: [PATCH v1 07/20] ARC: mm: use generic macros _BITUL() Noam Camus <noamc@ezchip.com> - 2015-11-02 07:30 +0100
  Re: [PATCH v1 07/20] ARC: mm: use generic macros _BITUL() Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-11-02 07:30 +0100
  Re: [PATCH v1 09/20] ARC: add CONFIG_CLKSRC_OF support to  time_init() Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-11-02 07:40 +0100
  Re: [PATCH v1 08/20] ARC: Use res_service as entry point for  secondaries Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-11-02 07:40 +0100
    RE: [PATCH v1 08/20] ARC: Use res_service as entry point for  secondaries Noam Camus <noamc@ezchip.com> - 2015-11-02 09:10 +0100
  Re: [PATCH v1 19/20] ARC: [plat-eznps] replace sync with proper cpu  barrier Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-11-02 08:50 +0100
    Re: [PATCH v1 19/20] ARC: [plat-eznps] replace sync with proper cpu  barrier Peter Zijlstra <peterz@infradead.org> - 2015-11-02 10:30 +0100
  Re: [PATCH v1 16/20] ARC: [plat-eznps] Use dedicated cpu_relax() Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-11-02 09:00 +0100
  Re: [PATCH v1 18/20] ARC: [plat-eznps] define IPI_IRQ Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-11-02 09:00 +0100
    RE: [PATCH v1 18/20] ARC: [plat-eznps] define IPI_IRQ Noam Camus <noamc@ezchip.com> - 2015-11-02 13:20 +0100
  Re: [PATCH v1 14/20] ARC: [plat-eznps] Use dedicated SMP barriers Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-11-02 09:10 +0100
    RE: [PATCH v1 14/20] ARC: [plat-eznps] Use dedicated SMP barriers Noam Camus <noamc@ezchip.com> - 2015-11-02 14:10 +0100
  Re: [PATCH v1 05/20] ARC: rwlock: disable interrupts in !LLSC variant Peter Zijlstra <peterz@infradead.org> - 2015-11-02 10:20 +0100
  Re: [PATCH v1 16/20] ARC: [plat-eznps] Use dedicated cpu_relax() Peter Zijlstra <peterz@infradead.org> - 2015-11-02 10:30 +0100
    RE: [PATCH v1 16/20] ARC: [plat-eznps] Use dedicated cpu_relax() Noam Camus <noamc@ezchip.com> - 2015-11-03 15:10 +0100
  Re: [PATCH v1 05/20] ARC: rwlock: disable interrupts in !LLSC variant Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-11-02 10:50 +0100
    Re: [PATCH v1 05/20] ARC: rwlock: disable interrupts in !LLSC variant Peter Zijlstra <peterz@infradead.org> - 2015-11-02 11:10 +0100
  Re: [PATCH v1 11/20] ARC: [plat-eznps] Add eznps platform Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-11-02 12:00 +0100
    RE: [PATCH v1 11/20] ARC: [plat-eznps] Add eznps platform Noam Camus <noamc@ezchip.com> - 2015-11-03 17:10 +0100
    RE: [PATCH v1 11/20] ARC: [plat-eznps] Add eznps platform Noam Camus <noamc@ezchip.com> - 2015-11-04 13:40 +0100
  Re: [PATCH v1 02/20] clocksource: Add NPS400 timers driver Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-11-02 12:10 +0100
    RE: [PATCH v1 02/20] clocksource: Add NPS400 timers driver Noam Camus <noamc@ezchip.com> - 2015-11-03 17:10 +0100
  Re: [PATCH v1 20/20] ARC: Add eznps platform to Kconfig and Makefile Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-11-02 12:10 +0100
    RE: [PATCH v1 20/20] ARC: Add eznps platform to Kconfig and Makefile Noam Camus <noamc@ezchip.com> - 2015-11-03 16:40 +0100
  Re: [PATCH v1 13/20] ARC: [plat-eznps] Use dedicated  bitops/atomic/cmpxchg Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-11-02 13:00 +0100
  Re: [PATCH v1 00/20] eznps a new ARC platform Vineet Gupta <vgupta@synopsys.com> - 2015-11-04 16:40 +0100
    RE: [PATCH v1 00/20] eznps a new ARC platform Noam Camus <noamc@ezchip.com> - 2015-11-04 17:00 +0100
      RE: [PATCH v1 00/20] eznps a new ARC platform Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-11-04 18:50 +0100
  Re: [PATCH v1 11/20] ARC: [plat-eznps] Add eznps platform Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-11-05 06:20 +0100
  Re: [PATCH v2 03/19] clocksource: Add NPS400 timers driver Thomas Gleixner <tglx@linutronix.de> - 2015-11-07 12:30 +0100
  Re: [PATCH v2 04/19] irqchip: add nps Internal and external  irqchips Thomas Gleixner <tglx@linutronix.de> - 2015-11-07 12:40 +0100
    Re: [PATCH v2 04/19] irqchip: add nps Internal and external irqchips Noam Camus <noamc@ezchip.com> - 2015-11-07 22:00 +0100
      Re: [PATCH v2 04/19] irqchip: add nps Internal and external  irqchips Thomas Gleixner <tglx@linutronix.de> - 2015-11-08 01:00 +0100
  Re: [PATCH v2 16/19] ARC: [plat-eznps] Use dedicated cpu_relax() Peter Zijlstra <peterz@infradead.org> - 2015-11-09 11:10 +0100
    Re: [PATCH v2 16/19] ARC: [plat-eznps] Use dedicated cpu_relax() Vineet Gupta <Vineet.Gupta1@synopsys.com> - 2015-11-09 11:30 +0100
      Re: [PATCH v2 16/19] ARC: [plat-eznps] Use dedicated cpu_relax() Peter Zijlstra <peterz@infradead.org> - 2015-11-09 11:50 +0100
        Re: [PATCH v2 16/19] ARC: [plat-eznps] Use dedicated cpu_relax() Vineet Gupta <vgupta@synopsys.com> - 2015-11-09 13:30 +0100
          Re: [PATCH v2 16/19] ARC: [plat-eznps] Use dedicated cpu_relax() Peter Zijlstra <peterz@infradead.org> - 2015-11-09 14:00 +0100

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