linux-kernel - Re: [PATCH] ARM: cache-v7: Disable preemption when reading CCSIDR

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Message-ID: <4F2B4873.5030808@codeaurora.org>
Date:	Thu, 02 Feb 2012 18:37:39 -0800
From:	Stephen Boyd <sboyd@...eaurora.org>
To:	Nicolas Pitre <nico@...xnic.net>
CC:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Catalin Marinas <catalin.marinas@....com>
Subject: Re: [PATCH] ARM: cache-v7: Disable preemption when reading CCSIDR

On 02/02/12 18:35, Nicolas Pitre wrote:
> On Thu, 2 Feb 2012, Stephen Boyd wrote:
>> On 02/02/12 17:18, Nicolas Pitre wrote:
>>> If you simply disable/restore IRQs around the critical region then you 
>>> don't have to worry about __v7_setup.  Plus this will allow for 
>>> v7_flush_dcache_all to still be callable from atomic context.
>> Ok. Here's a patch. I still need to test it. I'll send another patch
>> series to cleanup the get_thread_info stuff (there's two of them?).
>>
>>  arch/arm/mm/cache-v7.S |    6 ++++++
>>  1 files changed, 6 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/arm/mm/cache-v7.S b/arch/arm/mm/cache-v7.S
>> index 07c4bc8..654a5fc 100644
>> --- a/arch/arm/mm/cache-v7.S
>> +++ b/arch/arm/mm/cache-v7.S
>> @@ -54,9 +54,15 @@ loop1:
>>  	and	r1, r1, #7			@ mask of the bits for current cache only
>>  	cmp	r1, #2				@ see what cache we have at this level
>>  	blt	skip				@ skip if no cache, or just i-cache
>> +#ifdef CONFIG_PREEMPT
>> +	save_and_disable_irqs r9		@ make cssr&csidr read atomic
>> +#endif
>>  	mcr	p15, 2, r10, c0, c0, 0		@ select current cache level in cssr
>>  	isb					@ isb to sych the new cssr&csidr
>>  	mrc	p15, 1, r1, c0, c0, 0		@ read the new csidr
>> +#ifdef CONFIG_PREEMPT
>> +	restore_irqs r9
>> +#endif
> I'd suggest using restore_irqs_notrace instead.  The IRQ-off period is 
> so small that there is no point tracing it.

Thanks. I'll make sure to do that before uploading to the patch tracker.

-- 
Sent by an employee of the Qualcomm Innovation Center, Inc.
The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.

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