From: Sebastian Andrzej Siewior Date: Wed, 28 Jun 2023 09:36:10 +0200 Subject: [PATCH 3/4] ARM: vfp: Use vfp_lock() in vfp_support_entry(). Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.7/older/patches-6.7-rt6.tar.xz 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 --- arch/arm/vfp/vfpmodule.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) --- a/arch/arm/vfp/vfpmodule.c +++ b/arch/arm/vfp/vfpmodule.c @@ -708,7 +708,7 @@ 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); /* @@ -787,7 +787,7 @@ 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; @@ -797,7 +797,7 @@ bounce: regs->ARM_pc += 4; VFP_bounce(trigger, fpexc, regs); } - local_bh_enable(); + vfp_unlock(); return 0; }