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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Fri, 19 May 2023 16:57:30 +0200
Subject: [PATCH 2/4] ARM: vfp: Use vfp_lock() in vfp_sync_hwstate().
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.9/older/patches-6.9-rt5.tar.xz
vfp_sync_hwstate() uses preempt_disable() followed by local_bh_disable()
to ensure that it won't get interrupted while checking the VFP state.
This harms PREEMPT_RT because softirq handling can get preempted and
local_bh_disable() synchronizes the related section with a sleeping lock
which does not work with disabled preemption.
Use the vfp_lock() to synchronize the access.
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
arch/arm/vfp/vfpmodule.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -540,11 +540,9 @@ static inline void vfp_pm_init(void) { }
*/
void vfp_sync_hwstate(struct thread_info *thread)
{
- unsigned int cpu = get_cpu();
+ vfp_lock();
- local_bh_disable();
-
- if (vfp_state_in_hw(cpu, thread)) {
+ if (vfp_state_in_hw(raw_smp_processor_id(), thread)) {
u32 fpexc = fmrx(FPEXC);
/*
@@ -555,8 +553,7 @@ void vfp_sync_hwstate(struct thread_info
fmxr(FPEXC, fpexc);
}
- local_bh_enable();
- put_cpu();
+ vfp_unlock();
}
/* Ensure that the thread reloads the hardware VFP state on the next use. */
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