linux-kernel - [PATCH 4/6] sparc/mm: Do not disable preemption in lazy MMU mode

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Message-ID: <db1559396c38c1dfe97a6d929412d7d6244f64b8.1749747752.git.agordeev@linux.ibm.com>
Date: Thu, 12 Jun 2025 19:36:11 +0200
From: Alexander Gordeev <agordeev@...ux.ibm.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        sparclinux@...r.kernel.org, xen-devel@...ts.xenproject.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        Hugh Dickins <hughd@...gle.com>, Nicholas Piggin <npiggin@...il.com>,
        Guenter Roeck <linux@...ck-us.net>, Juergen Gross <jgross@...e.com>,
        Jeremy Fitzhardinge <jeremy@...p.org>,
        Ryan Roberts <ryan.roberts@....com>
Subject: [PATCH 4/6] sparc/mm: Do not disable preemption in lazy MMU mode

Commit a1d416bf9faf ("sparc/mm: disable preemption in lazy mmu mode")
is not necessary anymore, since the lazy MMU mode is entered with a
spinlock held and sparc does not support Real-Time. Thus, upon entering
the lazy mode the preemption is already disabled.

Signed-off-by: Alexander Gordeev <agordeev@...ux.ibm.com>
---
 arch/sparc/include/asm/tlbflush_64.h |  2 +-
 arch/sparc/mm/tlb.c                  | 12 ++++++++----
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/arch/sparc/include/asm/tlbflush_64.h b/arch/sparc/include/asm/tlbflush_64.h
index 8b8cdaa69272..a6d8068fb211 100644
--- a/arch/sparc/include/asm/tlbflush_64.h
+++ b/arch/sparc/include/asm/tlbflush_64.h
@@ -44,7 +44,7 @@ void flush_tlb_kernel_range(unsigned long start, unsigned long end);
 void flush_tlb_pending(void);
 void arch_enter_lazy_mmu_mode(void);
 void arch_leave_lazy_mmu_mode(void);
-#define arch_flush_lazy_mmu_mode()      do {} while (0)
+void arch_flush_lazy_mmu_mode(void);
 
 /* Local cpu only.  */
 void __flush_tlb_all(void);
diff --git a/arch/sparc/mm/tlb.c b/arch/sparc/mm/tlb.c
index a35ddcca5e76..e46dfd5f2583 100644
--- a/arch/sparc/mm/tlb.c
+++ b/arch/sparc/mm/tlb.c
@@ -52,10 +52,9 @@ void flush_tlb_pending(void)
 
 void arch_enter_lazy_mmu_mode(void)
 {
-	struct tlb_batch *tb;
+	struct tlb_batch *tb = this_cpu_ptr(&tlb_batch);
 
-	preempt_disable();
-	tb = this_cpu_ptr(&tlb_batch);
+	VM_WARN_ON_ONCE(preemptible());
 	tb->active = 1;
 }
 
@@ -63,10 +62,15 @@ void arch_leave_lazy_mmu_mode(void)
 {
 	struct tlb_batch *tb = this_cpu_ptr(&tlb_batch);
 
+	VM_WARN_ON_ONCE(preemptible());
 	if (tb->tlb_nr)
 		flush_tlb_pending();
 	tb->active = 0;
-	preempt_enable();
+}
+
+void arch_flush_lazy_mmu_mode(void)
+{
+	VM_WARN_ON_ONCE(preemptible());
 }
 
 static void tlb_batch_add_one(struct mm_struct *mm, unsigned long vaddr,
-- 
2.48.1