From: Paul Walmsley <pjw@kernel.org>
To: linux-riscv@lists.infradead.org
Subject: [PATCH 1/3] riscv: mm: pmdp_huge_get_and_clear(): avoid atomic ops when !CONFIG_SMP
Date: Wed, 19 Nov 2025 21:18:28 -0700 [thread overview]
Message-ID: <20251120042001.1766011-2-pjw@kernel.org> (raw)
In-Reply-To: <20251120042001.1766011-1-pjw@kernel.org>
When !CONFIG_SMP, there's no need for atomic operations in
pmdp_huge_get_and_clear(), so, similar to what x86 does, let's not use
atomics in this case. See also commit 546e42c8c6d94 ("riscv: Use an
atomic xchg in pudp_huge_get_and_clear()").
Cc: Alexandre Ghiti <alex@ghiti.fr>
Signed-off-by: Paul Walmsley <pjw@kernel.org>
---
arch/riscv/include/asm/pgtable.h | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 5a08eb5fe99f..64a2197e6d97 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -861,7 +861,13 @@ static inline int pmdp_test_and_clear_young(struct vm_area_struct *vma,
static inline pmd_t pmdp_huge_get_and_clear(struct mm_struct *mm,
unsigned long address, pmd_t *pmdp)
{
+#ifdef CONFIG_SMP
pmd_t pmd = __pmd(atomic_long_xchg((atomic_long_t *)pmdp, 0));
+#else
+ pmd_t pmd = *pmdp;
+
+ pmd_clear(pmdp);
+#endif
page_table_check_pmd_clear(mm, pmd);
--
2.48.1
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next prev parent reply other threads:[~2025-11-20 4:20 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-20 4:18 [PATCH 0/3] riscv: mm: clean up and optimize some page table get-and-clear functions Paul Walmsley
2025-11-20 4:18 ` Paul Walmsley [this message]
2025-11-20 4:18 ` [PATCH 2/3] riscv: mm: ptep_get_and_clear(): avoid atomic ops when !CONFIG_SMP Paul Walmsley
2025-11-20 4:18 ` [PATCH 3/3] riscv: mm: use xchg() on non-atomic_long_t variables, not atomic_long_xchg() Paul Walmsley
2025-11-20 4:30 ` [PATCH 0/3] riscv: mm: clean up and optimize some page table get-and-clear functions patchwork-bot+linux-riscv
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