4 files changed, 11 insertions, 68 deletions

diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
index 548b2c07ac9..86974c72d0d 100644
--- a/arch/x86/include/asm/i387.h
+++ b/arch/x86/include/asm/i387.h
@@ -30,7 +30,6 @@ extern void fpu_init(void);
 extern void mxcsr_feature_mask_init(void);
 extern int init_fpu(struct task_struct *child);
 extern void math_state_restore(void);
-extern void __math_state_restore(void);
 extern int dump_fpu(struct pt_regs *, struct user_i387_struct *);
 
 extern user_regset_active_fn fpregs_active, xfpregs_active;
diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 485204f58cd..324cd722b44 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -299,23 +299,11 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
                                  *next = &next_p->thread;
         int cpu = smp_processor_id();
         struct tss_struct *tss = &per_cpu(init_tss, cpu);
-        bool preload_fpu;
 
         /* never put a printk in __switch_to... printk() calls wake_up*() indirectly */
 
-        /*
-         * 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
-         */
-        preload_fpu = tsk_used_math(next_p) && next_p->fpu_counter > 5;
-
         __unlazy_fpu(prev_p);
 
-        /* we're going to use this soon, after a few expensive things */
-        if (preload_fpu)
-                prefetch(next->fpu.state);
-
         /*
          * Reload esp0.
          */
@@ -354,11 +342,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
                      task_thread_info(next_p)->flags & _TIF_WORK_CTXSW_NEXT))
                 __switch_to_xtra(prev_p, next_p, tss);
 
-        /* If we're going to preload the fpu context, make sure clts
-           is run while we're batching the cpu state updates. */
-        if (preload_fpu)
-                clts();
-
         /*
          * Leave lazy mode, flushing any hypercalls made here.
          * This must be done before restoring TLS segments so
@@ -368,9 +351,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
          */
         arch_end_context_switch(next_p);
 
-        if (preload_fpu)
-                __math_state_restore();
-
         /*
          * Restore %gs if needed (which is common)
          */
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c
index 9b9fe4a85c8..992b4e542bc 100644
--- a/arch/x86/kernel/process_64.c
+++ b/arch/x86/kernel/process_64.c
@@ -386,18 +386,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
         int cpu = smp_processor_id();
         struct tss_struct *tss = &per_cpu(init_tss, cpu);
         unsigned fsindex, gsindex;
-        bool preload_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
-         */
-        preload_fpu = tsk_used_math(next_p) && next_p->fpu_counter > 5;
-
-        /* we're going to use this soon, after a few expensive things */
-        if (preload_fpu)
-                prefetch(next->fpu.state);
 
         /*
          * Reload esp0, LDT and the page table pointer:
@@ -430,10 +418,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
         /* Must be after DS reload */
         __unlazy_fpu(prev_p);
 
-        /* Make sure cpu is ready for new context */
-        if (preload_fpu)
-                clts();
-
         /*
          * Leave lazy mode, flushing any hypercalls made here.
          * This must be done before restoring TLS segments so
@@ -492,13 +476,6 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
                      task_thread_info(prev_p)->flags & _TIF_WORK_CTXSW_PREV))
                 __switch_to_xtra(prev_p, next_p, tss);
 
-        /*
-         * Preload the FPU context, now that we've determined that the
-         * task is likely to be using it. 
-         */
-        if (preload_fpu)
-                __math_state_restore();
-
         return prev_p;
 }
 
diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
index fc676e44c77..5afe824c66e 100644
--- a/arch/x86/kernel/traps.c
+++ b/arch/x86/kernel/traps.c
@@ -571,28 +571,6 @@ asmlinkage void __attribute__((weak)) smp_threshold_interrupt(void)
 }
 
 /*
- * __math_state_restore assumes that cr0.TS is already clear and the
- * fpu state is all ready for use.  Used during context switch.
- */
-void __math_state_restore(void)
-{
-        struct thread_info *thread = current_thread_info();
-        struct task_struct *tsk = thread->task;
-
-        /*
-         * Paranoid restore. send a SIGSEGV if we fail to restore the state.
-         */
-        if (unlikely(restore_fpu_checking(tsk))) {
-                stts();
-                force_sig(SIGSEGV, tsk);
-                return;
-        }
-
-        __thread_set_has_fpu(thread);   /* clts in caller! */
-        tsk->fpu_counter++;
-}
-
-/*
  * 'math_state_restore()' saves the current math information in the
  * old math state array, and gets the new ones from the current task
  *
@@ -622,9 +600,18 @@ void math_state_restore(void)
                 local_irq_disable();
         }
 
-        clts();                         /* Allow maths ops (or we recurse) */
+        __thread_fpu_begin(thread);
 
-        __math_state_restore();
+        /*
+         * Paranoid restore. send a SIGSEGV if we fail to restore the state.
+         */
+        if (unlikely(restore_fpu_checking(tsk))) {
+                __thread_fpu_end(thread);
+                force_sig(SIGSEGV, tsk);
+                return;
+        }
+
+        tsk->fpu_counter++;
 }
 EXPORT_SYMBOL_GPL(math_state_restore);