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From f7f818b4021dbd63b610e1c28a2065bc0f4893db Mon Sep 17 00:00:00 2001
From: Valentin Schneider <valentin.schneider@arm.com>
Date: Wed, 11 Aug 2021 21:13:54 +0100
Subject: [PATCH 003/158] arm64: mm: Make arch_faults_on_old_pte() check for
migratability
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.15/older/patches-5.15.10-rt24.tar.xz
arch_faults_on_old_pte() relies on the calling context being
non-preemptible. CONFIG_PREEMPT_RT turns the PTE lock into a sleepable
spinlock, which doesn't disable preemption once acquired, triggering the
warning in arch_faults_on_old_pte().
It does however disable migration, ensuring the task remains on the same
CPU during the entirety of the critical section, making the read of
cpu_has_hw_af() safe and stable.
Make arch_faults_on_old_pte() check migratable() instead of preemptible().
Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20210811201354.1976839-5-valentin.schneider@arm.com
---
arch/arm64/include/asm/pgtable.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index 72f95c6a7051..30fe8c324ce6 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -1001,7 +1001,7 @@ static inline void update_mmu_cache(struct vm_area_struct *vma,
*/
static inline bool arch_faults_on_old_pte(void)
{
- WARN_ON(preemptible());
+ WARN_ON(is_migratable());
return !cpu_has_hw_af();
}
--
2.33.1
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