3 files changed, 18 insertions, 2 deletions

diff --git a/arch/i386/kernel/process.c b/arch/i386/kernel/process.c
index dd53c58f64f1..ae924c416b68 100644
--- a/arch/i386/kernel/process.c
+++ b/arch/i386/kernel/process.c
@@ -648,6 +648,11 @@ struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct tas
 
         __unlazy_fpu(prev_p);
 
+
+        /* we're going to use this soon, after a few expensive things */
+        if (next_p->fpu_counter > 5)
+                prefetch(&next->i387.fxsave);
+
         /*
          * Reload esp0.
          */
@@ -697,6 +702,13 @@ struct task_struct fastcall * __switch_to(struct task_struct *prev_p, struct tas
 
         disable_tsc(prev_p, next_p);
 
+        /* 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_p->fpu_counter > 5)
+                math_state_restore();
+
         return prev_p;
 }
 
diff --git a/arch/i386/kernel/traps.c b/arch/i386/kernel/traps.c
index f9bb1f89d687..4a6fa2837df2 100644
--- a/arch/i386/kernel/traps.c
+++ b/arch/i386/kernel/traps.c
@@ -1118,7 +1118,7 @@ fastcall unsigned long patch_espfix_desc(unsigned long uesp,
  * Must be called with kernel preemption disabled (in this case,
  * local interrupts are disabled at the call-site in entry.S).
  */
-asmlinkage void math_state_restore(struct pt_regs regs)
+asmlinkage void math_state_restore(void)
 {
         struct thread_info *thread = current_thread_info();
         struct task_struct *tsk = thread->task;
@@ -1128,6 +1128,7 @@ asmlinkage void math_state_restore(struct pt_regs regs)
                 init_fpu(tsk);
         restore_fpu(tsk);
         thread->status |= TS_USEDFPU;   /* So we fnsave on switch_to() */
+        tsk->fpu_counter++;
 }
 
 #ifndef CONFIG_MATH_EMULATION
diff --git a/include/asm-i386/i387.h b/include/asm-i386/i387.h
index bc1d6edae1ed..434936c732d6 100644
--- a/include/asm-i386/i387.h
+++ b/include/asm-i386/i387.h
@@ -76,7 +76,9 @@ static inline void __save_init_fpu( struct task_struct *tsk )
 
 #define __unlazy_fpu( tsk ) do { \
         if (task_thread_info(tsk)->status & TS_USEDFPU) \
-                save_init_fpu( tsk ); \
+                save_init_fpu( tsk );                   \
+        else                                            \
+                tsk->fpu_counter = 0;                   \
 } while (0)
 
 #define __clear_fpu( tsk )                                      \
@@ -118,6 +120,7 @@ static inline void save_init_fpu( struct task_struct *tsk )
 extern unsigned short get_fpu_cwd( struct task_struct *tsk );
 extern unsigned short get_fpu_swd( struct task_struct *tsk );
 extern unsigned short get_fpu_mxcsr( struct task_struct *tsk );
+extern asmlinkage void math_state_restore(void);
 
 /*
  * Signal frame handlers...