x86: move fpu_counter into ARCH specific thread_struct

Only a couple of arches (sh/x86) use fpu_counter in task_struct so it can
be moved out into ARCH specific thread_struct, reducing the size of
task_struct for other arches.

Compile tested i386_defconfig + gcc 4.7.3

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
Acked-by: Ingo Molnar <mingo@kernel.org>
Cc: Paul Mundt <paul.mundt@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/x86/include/asm/fpu-internal.h

@@ -365,7 +365,7 @@ static inline void drop_fpu(struct task_struct *tsk)
 	 * Forget coprocessor state..
 	 */
 	preempt_disable();
-	tsk->fpu_counter = 0;
+	tsk->thread.fpu_counter = 0;
 	__drop_fpu(tsk);
 	clear_used_math();
 	preempt_enable();
@@ -424,7 +424,7 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta
 	 * or if the past 5 consecutive context-switches used math.
 	 */
 	fpu.preload = tsk_used_math(new) && (use_eager_fpu() ||
-					     new->fpu_counter > 5);
+					     new->thread.fpu_counter > 5);
 	if (__thread_has_fpu(old)) {
 		if (!__save_init_fpu(old))
 			cpu = ~0;
@@ -433,16 +433,16 @@ static inline fpu_switch_t switch_fpu_prepare(struct task_struct *old, struct ta
 
 		/* Don't change CR0.TS if we just switch! */
 		if (fpu.preload) {
-			new->fpu_counter++;
+			new->thread.fpu_counter++;
 			__thread_set_has_fpu(new);
 			prefetch(new->thread.fpu.state);
 		} else if (!use_eager_fpu())
 			stts();
 	} else {
-		old->fpu_counter = 0;
+		old->thread.fpu_counter = 0;
 		old->thread.fpu.last_cpu = ~0;
 		if (fpu.preload) {
-			new->fpu_counter++;
+			new->thread.fpu_counter++;
 			if (!use_eager_fpu() && fpu_lazy_restore(new, cpu))
 				fpu.preload = 0;
 			else

arch/x86/include/asm/processor.h

@@ -488,6 +488,15 @@ struct thread_struct {
 	unsigned long		iopl;
 	/* Max allowed port in the bitmap, in bytes: */
 	unsigned		io_bitmap_max;
+	/*
+	 * fpu_counter contains the number of consecutive context switches
+	 * that the FPU is used. If this is over a threshold, the lazy fpu
+	 * saving becomes unlazy to save the trap. This is an unsigned char
+	 * so that after 256 times the counter wraps and the behavior turns
+	 * lazy again; this to deal with bursty apps that only use FPU for
+	 * a short time
+	 */
+	unsigned char fpu_counter;
 };
 
 /*

arch/x86/kernel/i387.c

@@ -100,7 +100,7 @@ void unlazy_fpu(struct task_struct *tsk)
 		__save_init_fpu(tsk);
 		__thread_fpu_end(tsk);
 	} else
-		tsk->fpu_counter = 0;
+		tsk->thread.fpu_counter = 0;
 	preempt_enable();
 }
 EXPORT_SYMBOL(unlazy_fpu);

arch/x86/kernel/process_32.c

@@ -153,7 +153,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
 		childregs->orig_ax = -1;
 		childregs->cs = __KERNEL_CS | get_kernel_rpl();
 		childregs->flags = X86_EFLAGS_IF | X86_EFLAGS_FIXED;
-		p->fpu_counter = 0;
+		p->thread.fpu_counter = 0;
 		p->thread.io_bitmap_ptr = NULL;
 		memset(p->thread.ptrace_bps, 0, sizeof(p->thread.ptrace_bps));
 		return 0;
@@ -166,7 +166,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
 	p->thread.ip = (unsigned long) ret_from_fork;
 	task_user_gs(p) = get_user_gs(current_pt_regs());
 
-	p->fpu_counter = 0;
+	p->thread.fpu_counter = 0;
 	p->thread.io_bitmap_ptr = NULL;
 	tsk = current;
 	err = -ENOMEM;

arch/x86/kernel/process_64.c

@@ -163,7 +163,7 @@ int copy_thread(unsigned long clone_flags, unsigned long sp,
 	p->thread.sp = (unsigned long) childregs;
 	p->thread.usersp = me->thread.usersp;
 	set_tsk_thread_flag(p, TIF_FORK);
-	p->fpu_counter = 0;
+	p->thread.fpu_counter = 0;
 	p->thread.io_bitmap_ptr = NULL;
 
 	savesegment(gs, p->thread.gsindex);

arch/x86/kernel/traps.c

@@ -653,7 +653,7 @@ void math_state_restore(void)
 		return;
 	}
 
-	tsk->fpu_counter++;
+	tsk->thread.fpu_counter++;
 }
 EXPORT_SYMBOL_GPL(math_state_restore);