Re: [PATCH v4 06/12] mm: enable MMU_GATHER_RCU_TABLE_FREE for sparc64
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From: Lance Yang <lance.yang@linux.dev>
Date: 2026-09-23 08:54:25
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On Tue, Sep 22, 2026 at 04:35:37PM +0100, Lorenzo Stoakes (ARM) wrote:
Commit 4a0100f7546f ("sparc64: use RCU page table freeing") enabled
CONFIG_MMU_GATHER_RCU_TABLE_FREE for SMP sparc64 architectures, expressly
for GUP-fast page table walkers.
Naturally, UP systems do not have to worry about concurrent GUP fast
operations.
However, CONFIG_PREEMPT_RCU is also available even on a UP system, so a
future pure-RCU page table walker requires MMU_GATHER_RCU_TABLE_FREE to be
enabled on UP, even if concurrent GUP fast is not possible there.
To enable future pure-RCU page table walkers, enable
MMU_GATHER_RCU_TABLE_FREE unconditionally.
With this change, it is no longer necessary to have !CONFIG_SMP
pgtable_free_tlb(), so also remove this now dead code.
This forms part of an overall effort to switch every architecture to this
mode.
Acked-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@kernel.org>
---Also ran page-table teardown stress on qemu-system-sparc64 (sun4u, UP). That ran cleanly too ;) Feel free to add: Tested-by: Lance Yang <lance.yang@linux.dev> Acked-by: Lance Yang <lance.yang@linux.dev>