From ead7db5eb90332deebf192183604bf5ec8e33c77 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 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(-) Index: linux-5.15/arch/arm64/include/asm/pgtable.h =================================================================== --- linux-5.15.orig/arch/arm64/include/asm/pgtable.h +++ linux-5.15/arch/arm64/include/asm/pgtable.h @@ -1001,7 +1001,7 @@ static inline void update_mmu_cache(stru */ static inline bool arch_faults_on_old_pte(void) { - WARN_ON(preemptible()); + WARN_ON(is_migratable()); return !cpu_has_hw_af(); }