1 files changed, 71 insertions, 56 deletions

diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index f25e7ec89416..0a96f71f0abd 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -33,7 +33,6 @@ void vfp_support_entry(void);
 void vfp_null_entry(void);
 
 void (*vfp_vector)(void) = vfp_null_entry;
-union vfp_state *last_VFP_context[NR_CPUS];
 
 /*
  * Dual-use variable.
@@ -43,6 +42,46 @@ union vfp_state *last_VFP_context[NR_CPUS];
 unsigned int VFP_arch;
 
 /*
+ * The pointer to the vfpstate structure of the thread which currently
+ * owns the context held in the VFP hardware, or NULL if the hardware
+ * context is invalid.
+ *
+ * For UP, this is sufficient to tell which thread owns the VFP context.
+ * However, for SMP, we also need to check the CPU number stored in the
+ * saved state too to catch migrations.
+ */
+union vfp_state *vfp_current_hw_state[NR_CPUS];
+
+/*
+ * Is 'thread's most up to date state stored in this CPUs hardware?
+ * Must be called from non-preemptible context.
+ */
+static bool vfp_state_in_hw(unsigned int cpu, struct thread_info *thread)
+{
+#ifdef CONFIG_SMP
+	if (thread->vfpstate.hard.cpu != cpu)
+		return false;
+#endif
+	return vfp_current_hw_state[cpu] == &thread->vfpstate;
+}
+
+/*
+ * Force a reload of the VFP context from the thread structure.  We do
+ * this by ensuring that access to the VFP hardware is disabled, and
+ * clear last_VFP_context.  Must be called from non-preemptible context.
+ */
+static void vfp_force_reload(unsigned int cpu, struct thread_info *thread)
+{
+	if (vfp_state_in_hw(cpu, thread)) {
+		fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
+		vfp_current_hw_state[cpu] = NULL;
+	}
+#ifdef CONFIG_SMP
+	thread->vfpstate.hard.cpu = NR_CPUS;
+#endif
+}
+
+/*
  * Per-thread VFP initialization.
  */
 static void vfp_thread_flush(struct thread_info *thread)
@@ -50,21 +89,27 @@ static void vfp_thread_flush(struct thread_info *thread)
 	union vfp_state *vfp = &thread->vfpstate;
 	unsigned int cpu;
 
-	memset(vfp, 0, sizeof(union vfp_state));
-
-	vfp->hard.fpexc = FPEXC_EN;
-	vfp->hard.fpscr = FPSCR_ROUND_NEAREST;
-
 	/*
 	 * Disable VFP to ensure we initialize it first.  We must ensure
-	 * that the modification of last_VFP_context[] and hardware disable
-	 * are done for the same CPU and without preemption.
+	 * that the modification of vfp_current_hw_state[] and hardware
+	 * disable are done for the same CPU and without preemption.
+	 *
+	 * Do this first to ensure that preemption won't overwrite our
+	 * state saving should access to the VFP be enabled at this point.
 	 */
 	cpu = get_cpu();
-	if (last_VFP_context[cpu] == vfp)
-		last_VFP_context[cpu] = NULL;
+	if (vfp_current_hw_state[cpu] == vfp)
+		vfp_current_hw_state[cpu] = NULL;
 	fmxr(FPEXC, fmrx(FPEXC) & ~FPEXC_EN);
 	put_cpu();
+
+	memset(vfp, 0, sizeof(union vfp_state));
+
+	vfp->hard.fpexc = FPEXC_EN;
+	vfp->hard.fpscr = FPSCR_ROUND_NEAREST;
+#ifdef CONFIG_SMP
+	vfp->hard.cpu = NR_CPUS;
+#endif
 }
 
 static void vfp_thread_exit(struct thread_info *thread)
@@ -73,8 +118,8 @@ static void vfp_thread_exit(struct thread_info *thread)
 	union vfp_state *vfp = &thread->vfpstate;
 	unsigned int cpu = get_cpu();
 
-	if (last_VFP_context[cpu] == vfp)
-		last_VFP_context[cpu] = NULL;
+	if (vfp_current_hw_state[cpu] == vfp)
+		vfp_current_hw_state[cpu] = NULL;
 	put_cpu();
 }
 
@@ -84,6 +129,9 @@ static void vfp_thread_copy(struct thread_info *thread)
 
 	vfp_sync_hwstate(parent);
 	thread->vfpstate = parent->vfpstate;
+#ifdef CONFIG_SMP
+	thread->vfpstate.hard.cpu = NR_CPUS;
+#endif
 }
 
 /*
@@ -129,17 +177,8 @@ static int vfp_notifier(struct notifier_block *self, unsigned long cmd, void *v)
 		 * case the thread migrates to a different CPU. The
 		 * restoring is done lazily.
 		 */
-		if ((fpexc & FPEXC_EN) && last_VFP_context[cpu]) {
-			vfp_save_state(last_VFP_context[cpu], fpexc);
-			last_VFP_context[cpu]->hard.cpu = cpu;
-		}
-		/*
-		 * Thread migration, just force the reloading of the
-		 * state on the new CPU in case the VFP registers
-		 * contain stale data.
-		 */
-		if (thread->vfpstate.hard.cpu != cpu)
-			last_VFP_context[cpu] = NULL;
+		if ((fpexc & FPEXC_EN) && vfp_current_hw_state[cpu])
+			vfp_save_state(vfp_current_hw_state[cpu], fpexc);
 #endif
 
 		/*
@@ -415,7 +454,7 @@ static int vfp_pm_suspend(void)
 	}
 
 	/* clear any information we had about last context state */
-	memset(last_VFP_context, 0, sizeof(last_VFP_context));
+	memset(vfp_current_hw_state, 0, sizeof(vfp_current_hw_state));
 
 	return 0;
 }
@@ -443,15 +482,15 @@ static void vfp_pm_init(void)
 static inline void vfp_pm_init(void) { }
 #endif /* CONFIG_PM */
 
+/*
+ * Ensure that the VFP state stored in 'thread->vfpstate' is up to date
+ * with the hardware state.
+ */
 void vfp_sync_hwstate(struct thread_info *thread)
 {
 	unsigned int cpu = get_cpu();
 
-	/*
-	 * If the thread we're interested in is the current owner of the
-	 * hardware VFP state, then we need to save its state.
-	 */
-	if (last_VFP_context[cpu] == &thread->vfpstate) {
+	if (vfp_state_in_hw(cpu, thread)) {
 		u32 fpexc = fmrx(FPEXC);
 
 		/*
@@ -465,36 +504,13 @@ void vfp_sync_hwstate(struct thread_info *thread)
 	put_cpu();
 }
 
+/* Ensure that the thread reloads the hardware VFP state on the next use. */
 void vfp_flush_hwstate(struct thread_info *thread)
 {
 	unsigned int cpu = get_cpu();
 
-	/*
-	 * If the thread we're interested in is the current owner of the
-	 * hardware VFP state, then we need to save its state.
-	 */
-	if (last_VFP_context[cpu] == &thread->vfpstate) {
-		u32 fpexc = fmrx(FPEXC);
-
-		fmxr(FPEXC, fpexc & ~FPEXC_EN);
-
-		/*
-		 * Set the context to NULL to force a reload the next time
-		 * the thread uses the VFP.
-		 */
-		last_VFP_context[cpu] = NULL;
-	}
+	vfp_force_reload(cpu, thread);
 
-#ifdef CONFIG_SMP
-	/*
-	 * For SMP we still have to take care of the case where the thread
-	 * migrates to another CPU and then back to the original CPU on which
-	 * the last VFP user is still the same thread. Mark the thread VFP
-	 * state as belonging to a non-existent CPU so that the saved one will
-	 * be reloaded in the above case.
-	 */
-	thread->vfpstate.hard.cpu = NR_CPUS;
-#endif
 	put_cpu();
 }
 
@@ -513,8 +529,7 @@ static int vfp_hotplug(struct notifier_block *b, unsigned long action,
 	void *hcpu)
 {
 	if (action == CPU_DYING || action == CPU_DYING_FROZEN) {
-		unsigned int cpu = (long)hcpu;
-		last_VFP_context[cpu] = NULL;
+		vfp_force_reload((long)hcpu, current_thread_info());
 	} else if (action == CPU_STARTING || action == CPU_STARTING_FROZEN)
 		vfp_enable(NULL);
 	return NOTIFY_OK;