1 files changed, 32 insertions, 10 deletions

diff --git a/arch/sh/kernel/process_32.c b/arch/sh/kernel/process_32.c
index 0673c4746be3..d8af889366a4 100644
--- a/arch/sh/kernel/process_32.c
+++ b/arch/sh/kernel/process_32.c
@@ -134,7 +134,10 @@ int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
         regs.regs[5] = (unsigned long)fn;
 
         regs.pc = (unsigned long)kernel_thread_helper;
-        regs.sr = (1 << 30);
+        regs.sr = SR_MD;
+#if defined(CONFIG_SH_FPU)
+        regs.sr |= SR_FD;
+#endif
 
         /* Ok, create the new process.. */
         pid = do_fork(flags | CLONE_VM | CLONE_UNTRACED, 0,
@@ -142,6 +145,7 @@ int kernel_thread(int (*fn)(void *), void * arg, unsigned long flags)
 
         return pid;
 }
+EXPORT_SYMBOL(kernel_thread);
 
 /*
  * Free current thread data structures etc..
@@ -186,6 +190,16 @@ int dump_fpu(struct pt_regs *regs, elf_fpregset_t *fpu)
 
         return fpvalid;
 }
+EXPORT_SYMBOL(dump_fpu);
+
+/*
+ * This gets called before we allocate a new thread and copy
+ * the current task into it.
+ */
+void prepare_to_copy(struct task_struct *tsk)
+{
+        unlazy_fpu(tsk, task_pt_regs(tsk));
+}
 
 asmlinkage void ret_from_fork(void);
 
@@ -195,16 +209,10 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
 {
         struct thread_info *ti = task_thread_info(p);
         struct pt_regs *childregs;
-#if defined(CONFIG_SH_FPU) || defined(CONFIG_SH_DSP)
+#if defined(CONFIG_SH_DSP)
         struct task_struct *tsk = current;
 #endif
 
-#if defined(CONFIG_SH_FPU)
-        unlazy_fpu(tsk, regs);
-        p->thread.fpu = tsk->thread.fpu;
-        copy_to_stopped_child_used_math(p);
-#endif
-
 #if defined(CONFIG_SH_DSP)
         if (is_dsp_enabled(tsk)) {
                 /* We can use the __save_dsp or just copy the struct:
@@ -224,6 +232,8 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
         } else {
                 childregs->regs[15] = (unsigned long)childregs;
                 ti->addr_limit = KERNEL_DS;
+                ti->status &= ~TS_USEDFPU;
+                p->fpu_counter = 0;
         }
 
         if (clone_flags & CLONE_SETTLS)
@@ -288,9 +298,13 @@ 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)
 {
-#if defined(CONFIG_SH_FPU)
+        struct thread_struct *next_t = &next->thread;
+
         unlazy_fpu(prev, task_pt_regs(prev));
-#endif
+
+        /* we're going to use this soon, after a few expensive things */
+        if (next->fpu_counter > 5)
+                prefetch(&next_t->fpu.hard);
 
 #ifdef CONFIG_MMU
         /*
@@ -321,6 +335,14 @@ __switch_to(struct task_struct *prev, struct task_struct *next)
 #endif
         }
 
+        /*
+         * 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));
+
         return prev;
 }