From 546e42c8c6d9498d5eac14bf2aca0383a11b145a Mon Sep 17 00:00:00 2001 From: Alexandre Ghiti Date: Tue, 23 Sep 2025 18:25:52 -0600 Subject: [PATCH] riscv: Use an atomic xchg in pudp_huge_get_and_clear() Make sure we return the right pud value and not a value that could have been overwritten in between by a different core. Fixes: c3cc2a4a3a23 ("riscv: Add support for PUD THP") Cc: stable@vger.kernel.org Signed-off-by: Alexandre Ghiti Link: https://lore.kernel.org/r/20250814-dev-alex-thp_pud_xchg-v1-1-b4704dfae206@rivosinc.com [pjw@kernel.org: use xchg rather than atomic_long_xchg; avoid atomic op for !CONFIG_SMP like x86] Signed-off-by: Paul Walmsley --- arch/riscv/include/asm/pgtable.h | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h index 91697fbf1f901..8150677429398 100644 --- a/arch/riscv/include/asm/pgtable.h +++ b/arch/riscv/include/asm/pgtable.h @@ -942,6 +942,23 @@ static inline int pudp_test_and_clear_young(struct vm_area_struct *vma, return ptep_test_and_clear_young(vma, address, (pte_t *)pudp); } +#define __HAVE_ARCH_PUDP_HUGE_GET_AND_CLEAR +static inline pud_t pudp_huge_get_and_clear(struct mm_struct *mm, + unsigned long address, pud_t *pudp) +{ +#ifdef CONFIG_SMP + pud_t pud = __pud(xchg(&pudp->pud, 0)); +#else + pud_t pud = *pudp; + + pud_clear(pudp); +#endif + + page_table_check_pud_clear(mm, pud); + + return pud; +} + static inline int pud_young(pud_t pud) { return pte_young(pud_pte(pud)); -- 2.39.5