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Commit c0c2803d authored by Ingo Molnar's avatar Ingo Molnar
Browse files

x86/fpu: Move thread_info::fpu_counter into thread_info::fpu.counter 



This field is kept separate from the main FPU state structure for
no good reason.

Reviewed-by: default avatarBorislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 3f6a0bce

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

+5 −5
Original line number Diff line number Diff line
@@ -384,7 +384,7 @@ static inline void drop_fpu(struct task_struct *tsk) 
	 * Forget coprocessor state..

	 */

	preempt_disable();

	tsk->thread.fpu_counter = 0;

	tsk->thread.fpu.counter = 0;



	if (__thread_has_fpu(tsk)) {

		/* Ignore delayed exceptions from user space */
@@ -441,7 +441,7 @@ 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->thread.fpu_counter > 5);

		      (use_eager_fpu() || new->thread.fpu.counter > 5);



	if (__thread_has_fpu(old)) {

		if (!__save_init_fpu(old))
@@ -454,16 +454,16 @@ 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->thread.fpu_counter++;

			new->thread.fpu.counter++;

			__thread_set_has_fpu(new);

			prefetch(new->thread.fpu.state);

		} else if (!use_eager_fpu())

			stts();

	} else {

		old->thread.fpu_counter = 0;

		old->thread.fpu.counter = 0;

		task_disable_lazy_fpu_restore(old);

		if (fpu.preload) {

			new->thread.fpu_counter++;

			new->thread.fpu.counter++;

			if (fpu_lazy_restore(new, cpu))

				fpu.preload = 0;

			else

arch/x86/include/asm/processor.h

+9 −9
Original line number Diff line number Diff line
@@ -433,6 +433,15 @@ struct fpu { 
	unsigned int last_cpu;

	unsigned int has_fpu;

	union thread_xstate *state;

	/*

	 * This 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 counter;

};



#ifdef CONFIG_X86_64
@@ -535,15 +544,6 @@ 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/process.c

+1 −1
Original line number Diff line number Diff line
@@ -87,7 +87,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) 
{

	*dst = *src;



	dst->thread.fpu_counter = 0;

	dst->thread.fpu.counter = 0;

	dst->thread.fpu.has_fpu = 0;

	dst->thread.fpu.state = NULL;

	task_disable_lazy_fpu_restore(dst);

arch/x86/kernel/traps.c

+1 −1
Original line number Diff line number Diff line
@@ -863,7 +863,7 @@ void math_state_restore(void) 
		fpu_reset_state(tsk);

		force_sig_info(SIGSEGV, SEND_SIG_PRIV, tsk);

	} else {

		tsk->thread.fpu_counter++;

		tsk->thread.fpu.counter++;

	}

	kernel_fpu_enable();

}