3 files changed, 31 insertions, 4 deletions
diff --git a/arch/sh/include/asm/fpu.h b/arch/sh/include/asm/fpu.h
index 1d3aee04b5c..bfd78e19de1 100644
--- a/arch/sh/include/asm/fpu.h
+++ b/arch/sh/include/asm/fpu.h
@@ -19,6 +19,7 @@ static inline void grab_fpu(struct pt_regs *regs)
 struct task_struct;
 
 extern void save_fpu(struct task_struct *__tsk, struct pt_regs *regs);
+void fpu_state_restore(struct pt_regs *regs);
 #else
 
 #define release_fpu(regs)	do { } while (0)
@@ -44,6 +45,8 @@ static inline void unlazy_fpu(struct task_struct *tsk, struct pt_regs *regs)
 	preempt_disable();
 	if (test_tsk_thread_flag(tsk, TIF_USEDFPU))
 		save_fpu(tsk, regs);
+	else
+		tsk->fpu_counter = 0;
 	preempt_enable();
 }
 
diff --git a/arch/sh/kernel/cpu/sh4/fpu.c b/arch/sh/kernel/cpu/sh4/fpu.c
index e3ea5411da6..d79226fa59d 100644
--- a/arch/sh/kernel/cpu/sh4/fpu.c
+++ b/arch/sh/kernel/cpu/sh4/fpu.c
@@ -483,18 +483,18 @@ BUILD_TRAP_HANDLER(fpu_error)
 	force_sig(SIGFPE, tsk);
 }
 
-BUILD_TRAP_HANDLER(fpu_state_restore)
+void fpu_state_restore(struct pt_regs *regs)
 {
 	struct task_struct *tsk = current;
-	TRAP_HANDLER_DECL;
 
 	grab_fpu(regs);
-	if (!user_mode(regs)) {
+	if (unlikely(!user_mode(regs))) {
 		printk(KERN_ERR "BUG: FPU is used in kernel mode.\n");
+		BUG();
 		return;
 	}
 
-	if (used_math()) {
+	if (likely(used_math())) {
 		/* Using the FPU again.  */
 		restore_fpu(tsk);
 	} else {
@@ -503,4 +503,12 @@ BUILD_TRAP_HANDLER(fpu_state_restore)
 		set_used_math();
 	}
 	set_tsk_thread_flag(tsk, TIF_USEDFPU);
+	tsk->fpu_counter++;
+}
+
+BUILD_TRAP_HANDLER(fpu_state_restore)
+{
+	TRAP_HANDLER_DECL;
+
+	fpu_state_restore(regs);
 }
diff --git a/arch/sh/kernel/process_32.c b/arch/sh/kernel/process_32.c
index 0673c4746be..aff5fe02e39 100644
--- a/arch/sh/kernel/process_32.c
+++ b/arch/sh/kernel/process_32.c
@@ -288,8 +288,14 @@ static void ubc_set_tracing(int asid, unsigned long pc)
 __notrace_funcgraph struct task_struct *
 __switch_to(struct task_struct *prev, struct task_struct *next)
 {
+	struct thread_struct *next_t = &next->thread;
+
 #if defined(CONFIG_SH_FPU)
 	unlazy_fpu(prev, task_pt_regs(prev));
+
+	/* we're going to use this soon, after a few expensive things */
+	if (next->fpu_counter > 5)
+		prefetch(&next_t->fpu.hard);
 #endif
 
 #ifdef CONFIG_MMU
@@ -321,6 +327,16 @@ __switch_to(struct task_struct *prev, struct task_struct *next)
 #endif
 	}
 
+#if defined(CONFIG_SH_FPU)
+	/* If the task has used fpu the last 5 timeslices, just do a full
+	 * restore of the math state immediately to avoid the trap; the
+	 * chances of needing FPU soon are obviously high now
+	 */
+	if (next->fpu_counter > 5) {
+		fpu_state_restore(task_pt_regs(next));
+	}
+#endif
+
 	return prev;
 }