ARM: 9424/1: vfp: Use vfp_state_hold() in vfp_sync_hwstate().

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_state_hold() to synchronize the access.

Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>

diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index 63de164..1726db0 100644 (file)
--- 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();
-
-       local_bh_disable();
+       vfp_state_hold();
 
-       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 *thread)
                fmxr(FPEXC, fpexc);
        }
 
-       local_bh_enable();
-       put_cpu();
+       vfp_state_release();
 }
 
 /* Ensure that the thread reloads the hardware VFP state on the next use. */