[PATCH 1/7] powerpc/85xx: re-enable timebase sync disabled by KEXEC patch

[Li Yang]

On Sat, Dec 4, 2010 at 12:40 AM, Kumar Gala <galak at kernel.crashing.org> wrote:
>
> On Dec 3, 2010, at 6:34 AM, Li Yang wrote:
>
>> The timebase sync is not only necessary when using KEXEC.  It should also
>> be used by normal boot up and cpu hotplug.  Remove the ifdef added by
>> the KEXEC patch.  Fix a problem that cpu hotplugging freezes the whole system.
>>
>> Signed-off-by: Jin Qing <b24347 at freescale.com>
>> Singed-off-by: Li Yang <leoli at freescale.com>
>> ---
>> arch/powerpc/platforms/85xx/smp.c |    4 +---
>> 1 files changed, 1 insertions(+), 3 deletions(-)
>
> But we have problems with KEXEC w/o this?  What is the issue with hotplugging and the generic timebase code?  When do we freeze?

Actually the KEXEC patch disables timebase sync when KEXEC is not
defined.  If the timebase sync is disabled, the timebase on non-boot
cpu will become non-consistent.  And thus ruins the scheduler when
hot-plugged.

>
>>
>> diff --git a/arch/powerpc/platforms/85xx/smp.c b/arch/powerpc/platforms/85xx/smp.c
>> index 5c91a99..1e8aec8 100644
>> --- a/arch/powerpc/platforms/85xx/smp.c
>> +++ b/arch/powerpc/platforms/85xx/smp.c
>> @@ -2,7 +2,7 @@
>>  * Author: Andy Fleming <afleming at freescale.com>
>>  *       Kumar Gala <galak at kernel.crashing.org>
>>  *
>> - * Copyright 2006-2008 Freescale Semiconductor Inc.
>> + * Copyright 2006-2010 Freescale Semiconductor Inc.
>>  *
>>  * This program is free software; you can redistribute  it and/or modify it
>>  * under  the terms of  the GNU General  Public License as published by the
>> @@ -115,10 +115,8 @@ smp_85xx_setup_cpu(int cpu_nr)
>>
>> struct smp_ops_t smp_85xx_ops = {
>>       .kick_cpu = smp_85xx_kick_cpu,
>> -#ifdef CONFIG_KEXEC
>>       .give_timebase  = smp_generic_give_timebase,
>>       .take_timebase  = smp_generic_take_timebase,
>> -#endif
>> };
>>
>> #ifdef CONFIG_KEXEC
>> --
>> 1.6.6-rc1.GIT
>>
>>
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>
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-- 
- Leo