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From 7f82f1bbba1f762468617387702002c0ca81df0f Mon Sep 17 00:00:00 2001
From: Imre Deak <imre.deak@nokia.com>
Date: Thu, 4 Feb 2010 21:38:02 +0200
Subject: [PATCH 31/32] ARM: VFP: add support to sync the VFP state of the current thread
ARM: VFP: add support to sync the VFP state of the current thread
So far vfp_sync_state worked only for threads other than the current
one. This worked for tracing other threads, but not for PTRACE_TRACEME.
Syncing for the current thread will also be needed by an upcoming patch
adding support for VFP context save / restore around signal handlers.
For SMP we need get_cpu now, since we have to protect the FPEXC
register, other than this things remained the same for threads other
than the current.
Signed-off-by: Imre Deak <imre.deak@nokia.com>
Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
---
arch/arm/vfp/vfpmodule.c | 46 +++++++++++++++++++++++++++++++---------------
1 files changed, 31 insertions(+), 15 deletions(-)
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index aed05bc..f28f45b 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -423,12 +423,19 @@ static inline void vfp_pm_init(void) { }
#endif /* CONFIG_PM */
/*
- * Synchronise the hardware VFP state of a thread other than current with the
- * saved one. This function is used by the ptrace mechanism.
+ * Synchronise the hardware VFP state of a thread with the saved one.
+ * This function is used by the ptrace mechanism and the signal handler path.
*/
-#ifdef CONFIG_SMP
void vfp_sync_state(struct thread_info *thread)
{
+ unsigned int cpu = get_cpu();
+ u32 fpexc = fmrx(FPEXC);
+ int vfp_enabled;
+ int self;
+
+ vfp_enabled = fpexc & FPEXC_EN;
+ self = thread == current_thread_info();
+#ifdef CONFIG_SMP
/*
* On SMP systems, the VFP state is automatically saved at every
* context switch. We mark the thread VFP state as belonging to a
@@ -436,18 +443,22 @@ void vfp_sync_state(struct thread_info *thread)
* needed.
*/
thread->vfpstate.hard.cpu = NR_CPUS;
-}
-#else
-void vfp_sync_state(struct thread_info *thread)
-{
- unsigned int cpu = get_cpu();
- u32 fpexc = fmrx(FPEXC);
-
/*
- * If VFP is enabled, the previous state was already saved and
- * last_VFP_context updated.
+ * Only the current thread's saved VFP context can be out-of-date.
+ * For others there is nothing else to do, since we already ensured
+ * force loading above.
*/
- if (fpexc & FPEXC_EN)
+ if (!self)
+ goto out;
+#endif
+ /*
+ * If the VFP is enabled only the current thread's saved VFP
+ * context can get out-of-date. For other threads the context
+ * was updated when the current thread started to use the VFP.
+ * This also means that the context will be reloaded next time
+ * the thread uses the VFP, so no need to enforce it.
+ */
+ if (vfp_enabled && !self)
goto out;
if (!last_VFP_context[cpu])
@@ -456,8 +467,14 @@ void vfp_sync_state(struct thread_info *thread)
/*
* Save the last VFP state on this CPU.
*/
- fmxr(FPEXC, fpexc | FPEXC_EN);
+ if (!vfp_enabled)
+ fmxr(FPEXC, fpexc | FPEXC_EN);
vfp_save_state(last_VFP_context[cpu], fpexc);
+ /*
+ * Disable VFP in case it was enabled so that the force reload
+ * can happen.
+ */
+ fpexc &= ~FPEXC_EN;
fmxr(FPEXC, fpexc);
/*
@@ -469,7 +486,6 @@ void vfp_sync_state(struct thread_info *thread)
out:
put_cpu();
}
-#endif
#include <linux/smp.h>
--
1.6.6.1
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