linux-kernel - Re: [PATCH V2 01/02] MIPS: Build uasm-generated code only once to avoid CPU Hotplug problem

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Message-ID: <514B2D0E.808@gmail.com>
Date:	Thu, 21 Mar 2013 08:53:50 -0700
From:	David Daney <ddaney.cavm@...il.com>
To:	Huacai Chen <chenhc@...ote.com>, Ralf Baechle <ralf@...ux-mips.org>
CC:	linux-mips@...ux-mips.org, linux-kernel@...r.kernel.org,
	Fuxin Zhang <zhangfx@...ote.com>,
	Zhangjin Wu <wuzhangjin@...il.com>,
	Hongbing Hu <huhb@...ote.com>
Subject: Re: [PATCH V2 01/02] MIPS: Build uasm-generated code only once to
 avoid CPU Hotplug problem

On 03/20/2013 04:14 PM, David Daney wrote:
> On 03/17/2013 05:49 AM, Huacai Chen wrote:
>> This and the next patch resolve memory corruption problems while CPU
>> hotplug. Without these patches, memory corruption can triggered easily
>> as below:
>>
[...]
>
> We were seeing the same crashes, this patch set seems to fix the problem.
>
> Acked-by: David Daney <david.daney@...ium.com>

On second thought...


>
>> ---
>>   arch/mips/include/asm/cpu-features.h               |    3 +++
>>   .../asm/mach-loongson/cpu-feature-overrides.h      |    1 +
>>   arch/mips/mm/page.c                                |   10 ++++++++++
>>   arch/mips/mm/tlbex.c                               |   10 ++++++++--
>>   4 files changed, 22 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/mips/include/asm/cpu-features.h
>> b/arch/mips/include/asm/cpu-features.h
>> index 1a57e8b..e5ec8fc 100644
>> --- a/arch/mips/include/asm/cpu-features.h
>> +++ b/arch/mips/include/asm/cpu-features.h
>> @@ -113,6 +113,9 @@
>>   #ifndef cpu_has_pindexed_dcache
>>   #define cpu_has_pindexed_dcache (cpu_data[0].dcache.flags &
>> MIPS_CACHE_PINDEX)
>>   #endif
>> +#ifndef cpu_has_local_ebase
>> +#define cpu_has_local_ebase    1


This really should default to 0 and only be set for (??who knows what??).

David Daney


>> +#endif
>>
>>   /*
>>    * I-Cache snoops remote store.     This only matters on SMP.  Some
>> multiprocessors
>> diff --git
>> a/arch/mips/include/asm/mach-loongson/cpu-feature-overrides.h
>> b/arch/mips/include/asm/mach-loongson/cpu-feature-overrides.h
>> index 75fd8c0..c0f3ef4 100644
>> --- a/arch/mips/include/asm/mach-loongson/cpu-feature-overrides.h
>> +++ b/arch/mips/include/asm/mach-loongson/cpu-feature-overrides.h
>> @@ -57,5 +57,6 @@
>>   #define cpu_has_vint        0
>>   #define cpu_has_vtag_icache    0
>>   #define cpu_has_watch        1
>> +#define cpu_has_local_ebase    0
>>
>>   #endif /* __ASM_MACH_LOONGSON_CPU_FEATURE_OVERRIDES_H */
>> diff --git a/arch/mips/mm/page.c b/arch/mips/mm/page.c
>> index a29fba5..4eb8dcf 100644
>> --- a/arch/mips/mm/page.c
>> +++ b/arch/mips/mm/page.c
>> @@ -247,6 +247,11 @@ void __cpuinit build_clear_page(void)
>>       struct uasm_label *l = labels;
>>       struct uasm_reloc *r = relocs;
>>       int i;
>> +    static atomic_t run_once = ATOMIC_INIT(0);
>> +
>> +    if (atomic_xchg(&run_once, 1)) {
>> +        return;
>> +    }
>>
>>       memset(labels, 0, sizeof(labels));
>>       memset(relocs, 0, sizeof(relocs));
>> @@ -389,6 +394,11 @@ void __cpuinit build_copy_page(void)
>>       struct uasm_label *l = labels;
>>       struct uasm_reloc *r = relocs;
>>       int i;
>> +    static atomic_t run_once = ATOMIC_INIT(0);
>> +
>> +    if (atomic_xchg(&run_once, 1)) {
>> +        return;
>> +    }
>>
>>       memset(labels, 0, sizeof(labels));
>>       memset(relocs, 0, sizeof(relocs));
>> diff --git a/arch/mips/mm/tlbex.c b/arch/mips/mm/tlbex.c
>> index 820e661..6bc28b4 100644
>> --- a/arch/mips/mm/tlbex.c
>> +++ b/arch/mips/mm/tlbex.c
>> @@ -2162,8 +2162,11 @@ void __cpuinit build_tlb_refill_handler(void)
>>       case CPU_TX3922:
>>       case CPU_TX3927:
>>   #ifndef CONFIG_MIPS_PGD_C0_CONTEXT
>> -        build_r3000_tlb_refill_handler();
>> +        if (cpu_has_local_ebase)
>> +            build_r3000_tlb_refill_handler();
>>           if (!run_once) {
>> +            if (!cpu_has_local_ebase)
>> +                build_r3000_tlb_refill_handler();
>>               build_r3000_tlb_load_handler();
>>               build_r3000_tlb_store_handler();
>>               build_r3000_tlb_modify_handler();
>> @@ -2192,9 +2195,12 @@ void __cpuinit build_tlb_refill_handler(void)
>>               build_r4000_tlb_load_handler();
>>               build_r4000_tlb_store_handler();
>>               build_r4000_tlb_modify_handler();
>> +            if (!cpu_has_local_ebase)
>> +                build_r4000_tlb_refill_handler();
>>               run_once++;
>>           }
>> -        build_r4000_tlb_refill_handler();
>> +        if (cpu_has_local_ebase)
>> +            build_r4000_tlb_refill_handler();
>>       }
>>   }
>>
>>
>

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