1 files changed, 16 insertions, 11 deletions

diff --git a/arch/x86/kernel/process_32.c b/arch/x86/kernel/process_32.c
index 59f4524984af..a80eddd41658 100644
--- a/arch/x86/kernel/process_32.c
+++ b/arch/x86/kernel/process_32.c
@@ -350,14 +350,21 @@ __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 */
 
-        __unlazy_fpu(prev_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
+         */
+        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 (next_p->fpu_counter > 5)
+        if (preload_fpu)
                 prefetch(next->xstate);
 
         /*
@@ -398,6 +405,11 @@ __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
@@ -407,15 +419,8 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p)
          */
         arch_end_context_switch(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
-         *
-         * tsk_used_math() checks prevent calling math_state_restore(),
-         * which can sleep in the case of !tsk_used_math()
-         */
-        if (tsk_used_math(next_p) && next_p->fpu_counter > 5)
-                math_state_restore();
+        if (preload_fpu)
+                __math_state_restore();
 
         /*
          * Restore %gs if needed (which is common)