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Re: [PATCH 2/3] PowerPC/mpc85xx: Add hotplug support on E5500 and E500MC cores

Started byScott Wood <scottwood@freescale.com>
First post2015-08-01 02:30 +0200
Last post2015-08-03 23:20 +0200
Articles 3 — 2 participants

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  Re: [PATCH 2/3] PowerPC/mpc85xx: Add hotplug support on E5500 and  E500MC cores Scott Wood <scottwood@freescale.com> - 2015-08-01 02:30 +0200
    Re: [PATCH 2/3] PowerPC/mpc85xx: Add hotplug support on E5500 and  E500MC cores Chenhui Zhao <chenhui.zhao@freescale.com> - 2015-08-03 14:00 +0200
      Re: [PATCH 2/3] PowerPC/mpc85xx: Add hotplug support on E5500 and  E500MC cores Scott Wood <scottwood@freescale.com> - 2015-08-03 23:20 +0200

#1197886 — Re: [PATCH 2/3] PowerPC/mpc85xx: Add hotplug support on E5500 and E500MC cores

FromScott Wood <scottwood@freescale.com>
Date2015-08-01 02:30 +0200
SubjectRe: [PATCH 2/3] PowerPC/mpc85xx: Add hotplug support on E5500 and E500MC cores
Message-ID<pSsQy-5bw-5@gated-at.bofh.it>
On Fri, 2015-07-31 at 17:20 +0800, b29983@freescale.com wrote:
> From: Tang Yuantian <Yuantian.Tang@freescale.com>
> 
> Freescale E500MC and E5500 core-based platforms, like P4080, T1040,
> support disabling/enabling CPU dynamically.
> This patch adds this feature on those platforms.
> 
> Signed-off-by: Chenhui Zhao <chenhui.zhao@freescale.com>
> Signed-off-by: Tang Yuantian <Yuantian.Tang@feescale.com>
> ---
>  arch/powerpc/Kconfig              |  2 +-
>  arch/powerpc/include/asm/smp.h    |  1 +
>  arch/powerpc/kernel/smp.c         |  5 +++++
>  arch/powerpc/platforms/85xx/smp.c | 39 ++++++++++++++++++++++++++++++++----
> ---
>  4 files changed, 39 insertions(+), 8 deletions(-)
> 
> diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> index 5ef2711..dd9e252 100644
> --- a/arch/powerpc/Kconfig
> +++ b/arch/powerpc/Kconfig
> @@ -386,7 +386,7 @@ config SWIOTLB
>  config HOTPLUG_CPU
>       bool "Support for enabling/disabling CPUs"
>       depends on SMP && (PPC_PSERIES || \
> -     PPC_PMAC || PPC_POWERNV || (PPC_85xx && !PPC_E500MC))
> +     PPC_PMAC || PPC_POWERNV || FSL_SOC_BOOKE)
>       ---help---
>         Say Y here to be able to disable and re-enable individual
>         CPUs at runtime on SMP machines.



> diff --git a/arch/powerpc/include/asm/smp.h b/arch/powerpc/include/asm/smp.h
> index 825663c..bf37d17 100644
> --- a/arch/powerpc/include/asm/smp.h
> +++ b/arch/powerpc/include/asm/smp.h
> @@ -67,6 +67,7 @@ void generic_cpu_die(unsigned int cpu);
>  void generic_set_cpu_dead(unsigned int cpu);
>  void generic_set_cpu_up(unsigned int cpu);
>  int generic_check_cpu_restart(unsigned int cpu);
> +int generic_check_cpu_dead(unsigned int cpu);
>  #endif
>  
>  #ifdef CONFIG_PPC64
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index ec9ec20..2cca27a 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -454,6 +454,11 @@ int generic_check_cpu_restart(unsigned int cpu)
>       return per_cpu(cpu_state, cpu) == CPU_UP_PREPARE;
>  }
>  
> +int generic_check_cpu_dead(unsigned int cpu)
> +{
> +     return per_cpu(cpu_state, cpu) == CPU_DEAD;
> +}

Is there a non-generic check_cpu_dead()?

It gets open-coded in generic_cpu_die()... Either open-code it elsewhere, or 
call it check_cpu_dead() and use it everywhere there's a CPU_DEAD check.


> +
>  static bool secondaries_inhibited(void)
>  {
>       return kvm_hv_mode_active();
> diff --git a/arch/powerpc/platforms/85xx/smp.c 
> b/arch/powerpc/platforms/85xx/smp.c
> index 6811a5b..7f0dadb 100644
> --- a/arch/powerpc/platforms/85xx/smp.c
> +++ b/arch/powerpc/platforms/85xx/smp.c
> @@ -42,6 +42,7 @@ struct epapr_spin_table {
>       u32     pir;
>  };
>  
> +#ifdef CONFIG_HOTPLUG_CPU
>  static u64 timebase;
>  static int tb_req;
>  static int tb_valid;
> @@ -111,7 +112,7 @@ static void mpc85xx_take_timebase(void)
>       local_irq_restore(flags);
>  }
>  
> -#ifdef CONFIG_HOTPLUG_CPU
> +#ifndef CONFIG_PPC_E500MC
>  static void e500_cpu_idle(void)

What happens if we bisect to patch 1/3 and run this on e500mc?

Please move the ifdef to that patch.

>  {
>       u32 tmp;
> @@ -127,6 +128,7 @@ static void e500_cpu_idle(void)
>       mtmsr(tmp);
>       isync();
>  }
> +#endif
>  
>  static void qoriq_cpu_dying(void)
>  {
> @@ -144,11 +146,30 @@ static void qoriq_cpu_dying(void)
>  
>       generic_set_cpu_dead(cpu);
>  
> +#ifndef CONFIG_PPC_E500MC
>       e500_cpu_idle();
> +#endif
>  
>       while (1)
>               ;
>  }
> +
> +static void qoriq_real_cpu_die(unsigned int cpu)

Real as opposed to...?

> +{
> +     int i;
> +
> +     for (i = 0; i < 50000; i++) {
> +             if (generic_check_cpu_dead(cpu)) {
> +                     qoriq_pm_ops->cpu_die(cpu);
> +#ifdef CONFIG_PPC64
> +                     paca[cpu].cpu_start = 0;
> +#endif
> +                     return;
> +             }
> +             udelay(10);
> +     }
> +     pr_err("%s: CPU%d didn't die...\n", __func__, cpu);
> +}

Only 500ms timeout, versus 10sec in generic_cpu_die()?

>  #endif
>  
>  static inline void flush_spin_table(void *spin_table)
> @@ -246,11 +267,7 @@ static int smp_85xx_kick_cpu(int nr)
>               spin_table = phys_to_virt(*cpu_rel_addr);
>  
>       local_irq_save(flags);
> -#ifdef CONFIG_PPC32
>  #ifdef CONFIG_HOTPLUG_CPU
> -     /* Corresponding to generic_set_cpu_dead() */
> -     generic_set_cpu_up(nr);
> -
>       if (system_state == SYSTEM_RUNNING) {
>               /*
>                * To keep it compatible with old boot program which uses
> @@ -263,6 +280,7 @@ static int smp_85xx_kick_cpu(int nr)
>               out_be32(&spin_table->addr_l, 0);
>               flush_spin_table(spin_table);
>  
> +             qoriq_pm_ops->cpu_up(nr);

Again, is it possible to get here without a valid qoriq_pm_ops (i.e. is there 
anything stopping the user from trying to initiate CPU hotplug)?

-Scott

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#1198784

FromChenhui Zhao <chenhui.zhao@freescale.com>
Date2015-08-03 14:00 +0200
Message-ID<pTmzo-29E-15@gated-at.bofh.it>
In reply to#1197886

On Sat, Aug 1, 2015 at 8:14 AM, Scott Wood <scottwood@freescale.com> 
wrote:
> On Fri, 2015-07-31 at 17:20 +0800, b29983@freescale.com wrote:
>>  From: Tang Yuantian <Yuantian.Tang@freescale.com>
>> 
>>  Freescale E500MC and E5500 core-based platforms, like P4080, T1040,
>>  support disabling/enabling CPU dynamically.
>>  This patch adds this feature on those platforms.
>> 
>>  Signed-off-by: Chenhui Zhao <chenhui.zhao@freescale.com>
>>  Signed-off-by: Tang Yuantian <Yuantian.Tang@feescale.com>
>>  ---
>>   arch/powerpc/Kconfig              |  2 +-
>>   arch/powerpc/include/asm/smp.h    |  1 +
>>   arch/powerpc/kernel/smp.c         |  5 +++++
>>   arch/powerpc/platforms/85xx/smp.c | 39 
>> ++++++++++++++++++++++++++++++++----
>>  ---
>>   4 files changed, 39 insertions(+), 8 deletions(-)
>> 
>>  diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
>>  index 5ef2711..dd9e252 100644
>>  --- a/arch/powerpc/Kconfig
>>  +++ b/arch/powerpc/Kconfig
>>  @@ -386,7 +386,7 @@ config SWIOTLB
>>   config HOTPLUG_CPU
>>        bool "Support for enabling/disabling CPUs"
>>        depends on SMP && (PPC_PSERIES || \
>>  -     PPC_PMAC || PPC_POWERNV || (PPC_85xx && !PPC_E500MC))
>>  +     PPC_PMAC || PPC_POWERNV || FSL_SOC_BOOKE)
>>        ---help---
>>          Say Y here to be able to disable and re-enable individual
>>          CPUs at runtime on SMP machines.
> 
> 
> 
>>  diff --git a/arch/powerpc/include/asm/smp.h 
>> b/arch/powerpc/include/asm/smp.h
>>  index 825663c..bf37d17 100644
>>  --- a/arch/powerpc/include/asm/smp.h
>>  +++ b/arch/powerpc/include/asm/smp.h
>>  @@ -67,6 +67,7 @@ void generic_cpu_die(unsigned int cpu);
>>   void generic_set_cpu_dead(unsigned int cpu);
>>   void generic_set_cpu_up(unsigned int cpu);
>>   int generic_check_cpu_restart(unsigned int cpu);
>>  +int generic_check_cpu_dead(unsigned int cpu);
>>   #endif
>> 
>>   #ifdef CONFIG_PPC64
>>  diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
>>  index ec9ec20..2cca27a 100644
>>  --- a/arch/powerpc/kernel/smp.c
>>  +++ b/arch/powerpc/kernel/smp.c
>>  @@ -454,6 +454,11 @@ int generic_check_cpu_restart(unsigned int cpu)
>>        return per_cpu(cpu_state, cpu) == CPU_UP_PREPARE;
>>   }
>> 
>>  +int generic_check_cpu_dead(unsigned int cpu)
>>  +{
>>  +     return per_cpu(cpu_state, cpu) == CPU_DEAD;
>>  +}
> 
> Is there a non-generic check_cpu_dead()?

NO, just follow the name "generic_check_cpu_restart()".

> 
> It gets open-coded in generic_cpu_die()... Either open-code it 
> elsewhere, or
> call it check_cpu_dead() and use it everywhere there's a CPU_DEAD 
> check.
> 
> 
>>  +
>>   static bool secondaries_inhibited(void)
>>   {
>>        return kvm_hv_mode_active();
>>  diff --git a/arch/powerpc/platforms/85xx/smp.c
>>  b/arch/powerpc/platforms/85xx/smp.c
>>  index 6811a5b..7f0dadb 100644
>>  --- a/arch/powerpc/platforms/85xx/smp.c
>>  +++ b/arch/powerpc/platforms/85xx/smp.c
>>  @@ -42,6 +42,7 @@ struct epapr_spin_table {
>>        u32     pir;
>>   };
>> 
>>  +#ifdef CONFIG_HOTPLUG_CPU
>>   static u64 timebase;
>>   static int tb_req;
>>   static int tb_valid;
>>  @@ -111,7 +112,7 @@ static void mpc85xx_take_timebase(void)
>>        local_irq_restore(flags);
>>   }
>> 
>>  -#ifdef CONFIG_HOTPLUG_CPU
>>  +#ifndef CONFIG_PPC_E500MC
>>   static void e500_cpu_idle(void)
> 
> What happens if we bisect to patch 1/3 and run this on e500mc?
> 
> Please move the ifdef to that patch.

OK.

> 
> 
>>   {
>>        u32 tmp;
>>  @@ -127,6 +128,7 @@ static void e500_cpu_idle(void)
>>        mtmsr(tmp);
>>        isync();
>>   }
>>  +#endif
>> 
>>   static void qoriq_cpu_dying(void)
>>   {
>>  @@ -144,11 +146,30 @@ static void qoriq_cpu_dying(void)
>> 
>>        generic_set_cpu_dead(cpu);
>> 
>>  +#ifndef CONFIG_PPC_E500MC
>>        e500_cpu_idle();
>>  +#endif
>> 
>>        while (1)
>>                ;
>>   }
>>  +
>>  +static void qoriq_real_cpu_die(unsigned int cpu)
> 
> Real as opposed to...?

It's hard to find a good name. :)

> 
> 
>>  +{
>>  +     int i;
>>  +
>>  +     for (i = 0; i < 50000; i++) {
>>  +             if (generic_check_cpu_dead(cpu)) {
>>  +                     qoriq_pm_ops->cpu_die(cpu);
>>  +#ifdef CONFIG_PPC64
>>  +                     paca[cpu].cpu_start = 0;
>>  +#endif
>>  +                     return;
>>  +             }
>>  +             udelay(10);
>>  +     }
>>  +     pr_err("%s: CPU%d didn't die...\n", __func__, cpu);
>>  +}
> 
> Only 500ms timeout, versus 10sec in generic_cpu_die()?

The process is fast. Maybe 10 second is too large.

> 
>>   #endif
>> 
>>   static inline void flush_spin_table(void *spin_table)
>>  @@ -246,11 +267,7 @@ static int smp_85xx_kick_cpu(int nr)
>>                spin_table = phys_to_virt(*cpu_rel_addr);
>> 
>>        local_irq_save(flags);
>>  -#ifdef CONFIG_PPC32
>>   #ifdef CONFIG_HOTPLUG_CPU
>>  -     /* Corresponding to generic_set_cpu_dead() */
>>  -     generic_set_cpu_up(nr);
>>  -
>>        if (system_state == SYSTEM_RUNNING) {
>>                /*
>>                 * To keep it compatible with old boot program which 
>> uses
>>  @@ -263,6 +280,7 @@ static int smp_85xx_kick_cpu(int nr)
>>                out_be32(&spin_table->addr_l, 0);
>>                flush_spin_table(spin_table);
>> 
>>  +             qoriq_pm_ops->cpu_up(nr);
> 
> Again, is it possible to get here without a valid qoriq_pm_ops (i.e. 
> is there
> anything stopping the user from trying to initiate CPU hotplug)?
> 
> -Scott

For every platform running this code, should has a valid qoriq_pm_ops. 
If not valid, it's a bug.

-Chenhui

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#1199271

FromScott Wood <scottwood@freescale.com>
Date2015-08-03 23:20 +0200
Message-ID<pTvjl-6An-13@gated-at.bofh.it>
In reply to#1198784
[Added linuxppc-dev@lists.ozlabs.org.  Besides that list being required for 
review of PPC patches, it feeds the patchwork that I use to track and apply 
patches.]

On Mon, 2015-08-03 at 19:52 +0800, Chenhui Zhao wrote:
> On Sat, Aug 1, 2015 at 8:14 AM, Scott Wood <scottwood@freescale.com> 
> wrote:
> > On Fri, 2015-07-31 at 17:20 +0800,  b29983@freescale.comwrote:
> > >  From: Tang Yuantian <Yuantian.Tang@freescale.com>
> > > 
> > >  Freescale E500MC and E5500 core-based platforms, like P4080, T1040,
> > >  support disabling/enabling CPU dynamically.
> > >  This patch adds this feature on those platforms.
> > > 
> > >  Signed-off-by: Chenhui Zhao <chenhui.zhao@freescale.com>
> > >  Signed-off-by: Tang Yuantian <Yuantian.Tang@feescale.com>
> > >  ---
> > >   arch/powerpc/Kconfig              |  2 +-
> > >   arch/powerpc/include/asm/smp.h    |  1 +
> > >   arch/powerpc/kernel/smp.c         |  5 +++++
> > >   arch/powerpc/platforms/85xx/smp.c | 39 
> > > ++++++++++++++++++++++++++++++++----
> > >  ---
> > >   4 files changed, 39 insertions(+), 8 deletions(-)
> > > 
> > >  diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
> > >  index 5ef2711..dd9e252 100644
> > >  --- a/arch/powerpc/Kconfig
> > >  +++ b/arch/powerpc/Kconfig
> > >  @@ -386,7 +386,7 @@ config SWIOTLB
> > >   config HOTPLUG_CPU
> > >        bool "Support for enabling/disabling CPUs"
> > >        depends on SMP && (PPC_PSERIES || \
> > >  -     PPC_PMAC || PPC_POWERNV || (PPC_85xx && !PPC_E500MC))
> > >  +     PPC_PMAC || PPC_POWERNV || FSL_SOC_BOOKE)
> > >        ---help---
> > >          Say Y here to be able to disable and re-enable individual
> > >          CPUs at runtime on SMP machines.
> > 
> > 
> > 
> > >  diff --git a/arch/powerpc/include/asm/smp.h 
> > > b/arch/powerpc/include/asm/smp.h
> > >  index 825663c..bf37d17 100644
> > >  --- a/arch/powerpc/include/asm/smp.h
> > >  +++ b/arch/powerpc/include/asm/smp.h
> > >  @@ -67,6 +67,7 @@ void generic_cpu_die(unsigned int cpu);
> > >   void generic_set_cpu_dead(unsigned int cpu);
> > >   void generic_set_cpu_up(unsigned int cpu);
> > >   int generic_check_cpu_restart(unsigned int cpu);
> > >  +int generic_check_cpu_dead(unsigned int cpu);
> > >   #endif
> > > 
> > >   #ifdef CONFIG_PPC64
> > >  diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> > >  index ec9ec20..2cca27a 100644
> > >  --- a/arch/powerpc/kernel/smp.c
> > >  +++ b/arch/powerpc/kernel/smp.c
> > >  @@ -454,6 +454,11 @@ int generic_check_cpu_restart(unsigned int cpu)
> > >        return per_cpu(cpu_state, cpu) == CPU_UP_PREPARE;
> > >   }
> > > 
> > >  +int generic_check_cpu_dead(unsigned int cpu)
> > >  +{
> > >  +     return per_cpu(cpu_state, cpu) == CPU_DEAD;
> > >  +}
> > 
> > Is there a non-generic check_cpu_dead()?
> 
> NO, just follow the name "generic_check_cpu_restart()".

But it's not the same situation as generic_check_cpu_restart().

> > It gets open-coded in generic_cpu_die()... Either open-code it 
> > elsewhere, or
> > call it check_cpu_dead() and use it everywhere there's a CPU_DEAD 
> > check.
> > 
> > 
> > >  +
> > >   static bool secondaries_inhibited(void)
> > >   {
> > >        return kvm_hv_mode_active();
> > >  diff --git a/arch/powerpc/platforms/85xx/smp.c
> > >  b/arch/powerpc/platforms/85xx/smp.c
> > >  index 6811a5b..7f0dadb 100644
> > >  --- a/arch/powerpc/platforms/85xx/smp.c
> > >  +++ b/arch/powerpc/platforms/85xx/smp.c
> > >  @@ -42,6 +42,7 @@ struct epapr_spin_table {
> > >        u32     pir;
> > >   };
> > > 
> > >  +#ifdef CONFIG_HOTPLUG_CPU
> > >   static u64 timebase;
> > >   static int tb_req;
> > >   static int tb_valid;
> > >  @@ -111,7 +112,7 @@ static void mpc85xx_take_timebase(void)
> > >        local_irq_restore(flags);
> > >   }
> > > 
> > >  -#ifdef CONFIG_HOTPLUG_CPU
> > >  +#ifndef CONFIG_PPC_E500MC
> > >   static void e500_cpu_idle(void)
> > 
> > What happens if we bisect to patch 1/3 and run this on e500mc?
> > 
> > Please move the ifdef to that patch.
> 
> OK.
> 
> > 
> > 
> > >   {
> > >        u32 tmp;
> > >  @@ -127,6 +128,7 @@ static void e500_cpu_idle(void)
> > >        mtmsr(tmp);
> > >        isync();
> > >   }
> > >  +#endif
> > > 
> > >   static void qoriq_cpu_dying(void)
> > >   {
> > >  @@ -144,11 +146,30 @@ static void qoriq_cpu_dying(void)
> > > 
> > >        generic_set_cpu_dead(cpu);
> > > 
> > >  +#ifndef CONFIG_PPC_E500MC
> > >        e500_cpu_idle();
> > >  +#endif
> > > 
> > >        while (1)
> > >                ;
> > >   }
> > >  +
> > >  +static void qoriq_real_cpu_die(unsigned int cpu)
> > 
> > Real as opposed to...?
> 
> It's hard to find a good name. :)

There are too many cpu_die() functions as is, and adding cpu_dying makes it 
worse.  Even just trying to come up with suggestions I've been having a hard 
time keeping track of which one goes in which ops struct.  This problem goes 
beyond the 85xx code, to the ridiculous and undocumented distinction between 
cpu_die() and __cpu_die().

It wouldn't be so bad if each layer were self contained, rather than multiple 
layers being defined in the same file.  I suggest keeping the existing 
convention whereby ppc_md.cpu_die ends in "_mach_cpu_die".  Don't call 
anything "cpu_dying".

I'd call qoriq_pm_ops->cpu_die something else (e.g. cpu_kill) even though it 
is in a separate file, just because of how confused and overused the name is 
elsewhere.


> +{
> > >  +     int i;
> > >  +
> > >  +     for (i = 0; i < 50000; i++) {
> > >  +             if (generic_check_cpu_dead(cpu)) {
> > >  +                     qoriq_pm_ops->cpu_die(cpu);
> > >  +#ifdef CONFIG_PPC64
> > >  +                     paca[cpu].cpu_start = 0;
> > >  +#endif
> > >  +                     return;
> > >  +             }
> > >  +             udelay(10);
> > >  +     }
> > >  +     pr_err("%s: CPU%d didn't die...\n", __func__, cpu);
> > >  +}
> > 
> > Only 500ms timeout, versus 10sec in generic_cpu_die()?
> 
> The process is fast. Maybe 10 second is too large.

Is it fast 100% of the time?  What if the CPU you intend to die is in a long 
critical section?  What harm is there to having a longer timeout, similar to 
what other platforms use?

> 
> > 
> > >   #endif
> > > 
> > >   static inline void flush_spin_table(void *spin_table)
> > >  @@ -246,11 +267,7 @@ static int smp_85xx_kick_cpu(int nr)
> > >                spin_table = phys_to_virt(*cpu_rel_addr);
> > > 
> > >        local_irq_save(flags);
> > >  -#ifdef CONFIG_PPC32
> > >   #ifdef CONFIG_HOTPLUG_CPU
> > >  -     /* Corresponding to generic_set_cpu_dead() */
> > >  -     generic_set_cpu_up(nr);
> > >  -
> > >        if (system_state == SYSTEM_RUNNING) {
> > >                /*
> > >                 * To keep it compatible with old boot program which 
> > > uses
> > >  @@ -263,6 +280,7 @@ static int smp_85xx_kick_cpu(int nr)
> > >                out_be32(&spin_table->addr_l, 0);
> > >                flush_spin_table(spin_table);
> > > 
> > >  +             qoriq_pm_ops->cpu_up(nr);
> > 
> > Again, is it possible to get here without a valid qoriq_pm_ops (i.e. 
> > is there
> > anything stopping the user from trying to initiate CPU hotplug)?
> > 
> > -Scott
> 
> For every platform running this code, should has a valid qoriq_pm_ops. 
> If not valid, it's a bug.

How do you prevent this code from running when there is no valid qoriq_pm_ops?

-Scott


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