From 48eb2a8541222453ad3b9137dd889990aff5ad47 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Date: Tue, 23 Jan 2024 12:56:21 +0100 Subject: [PATCH 63/64] arm: Disable FAST_GUP on PREEMPT_RT if HIGHPTE is also enabled. gup_pgd_range() is invoked with disabled interrupts and invokes __kmap_local_page_prot() via pte_offset_map(), gup_p4d_range(). With HIGHPTE enabled, __kmap_local_page_prot() invokes kmap_high_get() which uses a spinlock_t via lock_kmap_any(). This leads to an sleeping-while-atomic error on PREEMPT_RT because spinlock_t becomes a sleeping lock and must not be acquired in atomic context. The loop in map_new_virtual() uses wait_queue_head_t for wake up which also is using a spinlock_t. Limit HAVE_FAST_GUP additionaly to remain disabled on PREEMPT_RT with HIGHPTE enabled. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> (cherry picked from commit 02cf5a345530b4d3a94093f0b5c784701c2e7c6a) Signed-off-by: Clark Williams <clark.williams@gmail.com> --- arch/arm/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) Index: linux-6.1.96-rt35/arch/arm/Kconfig =================================================================== @ linux-6.1.96-rt35/arch/arm/Kconfig:98 @ config ARM select HAVE_DYNAMIC_FTRACE_WITH_REGS if HAVE_DYNAMIC_FTRACE select HAVE_EFFICIENT_UNALIGNED_ACCESS if (CPU_V6 || CPU_V6K || CPU_V7) && MMU select HAVE_EXIT_THREAD - select HAVE_FAST_GUP if ARM_LPAE + select HAVE_FAST_GUP if ARM_LPAE && !(PREEMPT_RT && HIGHPTE) select HAVE_FTRACE_MCOUNT_RECORD if !XIP_KERNEL select HAVE_FUNCTION_GRAPH_TRACER select HAVE_FUNCTION_TRACER if !XIP_KERNEL