From 837412fb4995c1e8c5dd9419c818db1d8700505b Mon Sep 17 00:00:00 2001
From: Chuck Ebbert <76306.1226@compuserve.com>
Date: Thu, 7 Dec 2006 02:14:01 +0100
Subject: [PATCH] --- yaml --- r: 43008 b: refs/heads/master c:
 acc207616a91a413a50fdd8847a747c4a7324167 h: refs/heads/master v: v3

---
 [refs]                           |  2 +-
 trunk/arch/i386/kernel/process.c | 12 ++++++++++++
 trunk/arch/i386/kernel/traps.c   |  3 ++-
 trunk/include/asm-i386/i387.h    |  5 ++++-
 4 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/[refs] b/[refs]
index 1db8a15561eb..fd64d91e0d6d 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: be44d2aabce2d62f72d5751d1871b6212bf7a1c7
+refs/heads/master: acc207616a91a413a50fdd8847a747c4a7324167
diff --git a/trunk/arch/i386/kernel/process.c b/trunk/arch/i386/kernel/process.c
index dd53c58f64f1..ae924c416b68 100644
--- a/trunk/arch/i386/kernel/process.c
+++ b/trunk/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/trunk/arch/i386/kernel/traps.c b/trunk/arch/i386/kernel/traps.c
index f9bb1f89d687..4a6fa2837df2 100644
--- a/trunk/arch/i386/kernel/traps.c
+++ b/trunk/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/trunk/include/asm-i386/i387.h b/trunk/include/asm-i386/i387.h
index bc1d6edae1ed..434936c732d6 100644
--- a/trunk/include/asm-i386/i387.h
+++ b/trunk/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...