From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Wed, 28 Jun 2023 09:36:10 +0200
Subject: [PATCH 3/4] ARM: vfp: Use vfp_lock() in vfp_support_entry().

vfp_entry() is invoked from exception handler and is fully preemptible.
It uses local_bh_disable() to remain uninterrupted while checking the
VFP state.
This is not working on PREEMPT_RT because local_bh_disable()
synchronizes the relevant section but the context remains fully
preemptible.

Use vfp_lock() for uninterrupted access.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 arch/arm/vfp/vfpmodule.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

Index: linux-6.8.2-rt10/arch/arm/vfp/vfpmodule.c
===================================================================
@ linux-6.8.2-rt10/arch/arm/vfp/vfpmodule.c:711 @ static int vfp_support_entry(struct pt_r
 	if (!user_mode(regs))
 		return vfp_kmode_exception(regs, trigger);
 
-	local_bh_disable();
+	vfp_lock();
 	fpexc = fmrx(FPEXC);
 
 	/*
@ linux-6.8.2-rt10/arch/arm/vfp/vfpmodule.c:790 @ static int vfp_support_entry(struct pt_r
 			if (!(fpscr & FPSCR_IXE)) {
 				if (!(fpscr & FPSCR_LENGTH_MASK)) {
 					pr_debug("not VFP\n");
-					local_bh_enable();
+					vfp_unlock();
 					return -ENOEXEC;
 				}
 				fpexc |= FPEXC_DEX;
@ linux-6.8.2-rt10/arch/arm/vfp/vfpmodule.c:800 @ bounce:		regs->ARM_pc += 4;
 		VFP_bounce(trigger, fpexc, regs);
 	}
 
-	local_bh_enable();
+	vfp_unlock();
 	return 0;
 }