[PATCH v4 08/12] arm64: mm: replace TIF_LAZY_MMU with in_lazy_mmu_mode()

[David Hildenbrand]

On 29.10.25 11:09, 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.
> 
> Signed-off-by: Kevin Brodsky <kevin.brodsky at arm.com>
> ---
>   arch/arm64/include/asm/pgtable.h     | 16 +++-------------
>   arch/arm64/include/asm/thread_info.h |  3 +--
>   2 files changed, 4 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
> index 535435248923..61ca88f94551 100644
> --- a/arch/arm64/include/asm/pgtable.h
> +++ b/arch/arm64/include/asm/pgtable.h
> @@ -62,30 +62,21 @@ 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)) {
> -		/* Avoid the atomic op if already set. */
> -		if (!(flags & BIT(TIF_LAZY_MMU_PENDING)))
> -			set_thread_flag(TIF_LAZY_MMU_PENDING);
> -	} else {
> +	if (in_lazy_mmu_mode())
> +		test_and_set_thread_flag(TIF_LAZY_MMU_PENDING);

You likely don't want a test_and_set here, which would do a 
test_and_set_bit() -- an atomic rmw.

You only want to avoid the atomic write if already set.

So keep the current

	/* Avoid the atomic op if already set. */
	if (!(flags & BIT(TIF_LAZY_MMU_PENDING)))
		set_thread_flag(TIF_LAZY_MMU_PENDING);

-- 
Cheers

David