Re: [PATCH v5 09/12] arm64: mm: replace TIF_LAZY_MMU with in_lazy_mmu_mode()

["David Hildenbrand (Red Hat)" <david@kernel.org>]

On 12/4/25 07:52, Anshuman Khandual wrote:
> On 24/11/25 6:52 PM, Kevin Brodsky wrote:
>> The generic lazy_mmu layer now tracks whether a task is in lazy MMU
>> mode. As a result we no longer need a TIF flag for that purpose -
>> let's use the new in_lazy_mmu_mode() helper instead.
>>
>> The explicit check for in_interrupt() is no longer necessary either
>> as in_lazy_mmu_mode() always returns false in interrupt context.
>>
>> Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
>> ---
>>   arch/arm64/include/asm/pgtable.h     | 19 +++----------------
>>   arch/arm64/include/asm/thread_info.h |  3 +--
>>   2 files changed, 4 insertions(+), 18 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
>> index a7d99dee3dc4..dd7ed653a20d 100644
>> --- a/arch/arm64/include/asm/pgtable.h
>> +++ b/arch/arm64/include/asm/pgtable.h
>> @@ -62,28 +62,16 @@ static inline void emit_pte_barriers(void)
>>   
>>   static inline void queue_pte_barriers(void)
>>   {
>> -	unsigned long flags;
>> -
>> -	if (in_interrupt()) {
>> -		emit_pte_barriers();
>> -		return;
>> -	}
>> -
>> -	flags = read_thread_flags();
>> -
>> -	if (flags & BIT(TIF_LAZY_MMU)) {
>> +	if (in_lazy_mmu_mode()) {
>>   		/* Avoid the atomic op if already set. */
>> -		if (!(flags & BIT(TIF_LAZY_MMU_PENDING)))
>> +		if (!test_thread_flag(TIF_LAZY_MMU_PENDING))
> 
> A small nit - will it be better not to use test_thread_flag() here and just
> keep checking flags like earlier to avoid non-related changes. Although not
> a problem TBH.

I'd assume the existing code wanted to avoid fetching the flags two 
times? So switching to test_thread_flag() should be fine now.

-- 
Cheers

David