Commit 6478d880 authored by Ingo Molnar's avatar Ingo Molnar
Browse files

sched: remove the !PREEMPT_BKL code 



remove the !PREEMPT_BKL code.

this removes 160 lines of legacy code.

Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 58b8a73a

include/linux/hardirq.h

+1 −5
Original line number Diff line number Diff line
@@ -72,11 +72,7 @@ 
#define in_softirq()		(softirq_count())

#define in_interrupt()		(irq_count())



#if defined(CONFIG_PREEMPT) && !defined(CONFIG_PREEMPT_BKL)

# define in_atomic()	((preempt_count() & ~PREEMPT_ACTIVE) != kernel_locked())

#else

#define in_atomic()		((preempt_count() & ~PREEMPT_ACTIVE) != 0)

#endif



#ifdef CONFIG_PREEMPT

# define PREEMPT_CHECK_OFFSET 1

include/linux/smp_lock.h

+1 −13
Original line number Diff line number Diff line
@@ -17,22 +17,10 @@ extern void __lockfunc __release_kernel_lock(void); 
		__release_kernel_lock();	\

} while (0)



/*

 * Non-SMP kernels will never block on the kernel lock,

 * so we are better off returning a constant zero from

 * reacquire_kernel_lock() so that the compiler can see

 * it at compile-time.

 */

#if defined(CONFIG_SMP) && !defined(CONFIG_PREEMPT_BKL)

# define return_value_on_smp return

#else

# define return_value_on_smp

#endif



static inline int reacquire_kernel_lock(struct task_struct *task)

{

	if (unlikely(task->lock_depth >= 0))

		return_value_on_smp __reacquire_kernel_lock();

		return __reacquire_kernel_lock();

	return 0;

}

kernel/Kconfig.preempt

+0 −4
Original line number Diff line number Diff line
@@ -52,10 +52,6 @@ config PREEMPT 


endchoice



config PREEMPT_BKL

	def_bool y

	depends on SMP || PREEMPT



config RCU_TRACE

	bool "Enable tracing for RCU - currently stats in debugfs"

	select DEBUG_FS

kernel/sched.c

+3 −16
Original line number Diff line number Diff line
@@ -3955,10 +3955,9 @@ EXPORT_SYMBOL(schedule); 
asmlinkage void __sched preempt_schedule(void)

{

	struct thread_info *ti = current_thread_info();

#ifdef CONFIG_PREEMPT_BKL

	struct task_struct *task = current;

	int saved_lock_depth;

#endif



	/*

	 * If there is a non-zero preempt_count or interrupts are disabled,

	 * we do not want to preempt the current task. Just return..
@@ -3974,14 +3973,10 @@ asmlinkage void __sched preempt_schedule(void) 
		 * clear ->lock_depth so that schedule() doesnt

		 * auto-release the semaphore:

		 */

#ifdef CONFIG_PREEMPT_BKL

		saved_lock_depth = task->lock_depth;

		task->lock_depth = -1;

#endif

		schedule();

#ifdef CONFIG_PREEMPT_BKL

		task->lock_depth = saved_lock_depth;

#endif

		sub_preempt_count(PREEMPT_ACTIVE);



		/*
@@ -4002,10 +3997,9 @@ EXPORT_SYMBOL(preempt_schedule); 
asmlinkage void __sched preempt_schedule_irq(void)

{

	struct thread_info *ti = current_thread_info();

#ifdef CONFIG_PREEMPT_BKL

	struct task_struct *task = current;

	int saved_lock_depth;

#endif



	/* Catch callers which need to be fixed */

	BUG_ON(ti->preempt_count || !irqs_disabled());
@@ -4017,16 +4011,12 @@ asmlinkage void __sched preempt_schedule_irq(void) 
		 * clear ->lock_depth so that schedule() doesnt

		 * auto-release the semaphore:

		 */

#ifdef CONFIG_PREEMPT_BKL

		saved_lock_depth = task->lock_depth;

		task->lock_depth = -1;

#endif

		local_irq_enable();

		schedule();

		local_irq_disable();

#ifdef CONFIG_PREEMPT_BKL

		task->lock_depth = saved_lock_depth;

#endif

		sub_preempt_count(PREEMPT_ACTIVE);



		/*
@@ -5241,11 +5231,8 @@ void __cpuinit init_idle(struct task_struct *idle, int cpu) 
	spin_unlock_irqrestore(&rq->lock, flags);



	/* Set the preempt count _outside_ the spinlocks! */

#if defined(CONFIG_PREEMPT) && !defined(CONFIG_PREEMPT_BKL)

	task_thread_info(idle)->preempt_count = (idle->lock_depth >= 0);

#else

	task_thread_info(idle)->preempt_count = 0;

#endif



	/*

	 * The idle tasks have their own, simple scheduling class:

	 */

lib/kernel_lock.c

+0 −123
Original line number Diff line number Diff line
@@ -9,7 +9,6 @@ 
#include <linux/module.h>

#include <linux/kallsyms.h>



#ifdef CONFIG_PREEMPT_BKL

/*

 * The 'big kernel semaphore'

 *
@@ -86,128 +85,6 @@ void __lockfunc unlock_kernel(void) 
		up(&kernel_sem);

}



#else



/*

 * The 'big kernel lock'

 *

 * This spinlock is taken and released recursively by lock_kernel()

 * and unlock_kernel().  It is transparently dropped and reacquired

 * over schedule().  It is used to protect legacy code that hasn't

 * been migrated to a proper locking design yet.

 *

 * Don't use in new code.

 */

static  __cacheline_aligned_in_smp DEFINE_SPINLOCK(kernel_flag);





/*

 * Acquire/release the underlying lock from the scheduler.

 *

 * This is called with preemption disabled, and should

 * return an error value if it cannot get the lock and

 * TIF_NEED_RESCHED gets set.

 *

 * If it successfully gets the lock, it should increment

 * the preemption count like any spinlock does.

 *

 * (This works on UP too - _raw_spin_trylock will never

 * return false in that case)

 */

int __lockfunc __reacquire_kernel_lock(void)

{

	while (!_raw_spin_trylock(&kernel_flag)) {

		if (test_thread_flag(TIF_NEED_RESCHED))

			return -EAGAIN;

		cpu_relax();

	}

	preempt_disable();

	return 0;

}



void __lockfunc __release_kernel_lock(void)

{

	_raw_spin_unlock(&kernel_flag);

	preempt_enable_no_resched();

}



/*

 * These are the BKL spinlocks - we try to be polite about preemption. 

 * If SMP is not on (ie UP preemption), this all goes away because the

 * _raw_spin_trylock() will always succeed.

 */

#ifdef CONFIG_PREEMPT

static inline void __lock_kernel(void)

{

	preempt_disable();

	if (unlikely(!_raw_spin_trylock(&kernel_flag))) {

		/*

		 * If preemption was disabled even before this

		 * was called, there's nothing we can be polite

		 * about - just spin.

		 */

		if (preempt_count() > 1) {

			_raw_spin_lock(&kernel_flag);

			return;

		}



		/*

		 * Otherwise, let's wait for the kernel lock

		 * with preemption enabled..

		 */

		do {

			preempt_enable();

			while (spin_is_locked(&kernel_flag))

				cpu_relax();

			preempt_disable();

		} while (!_raw_spin_trylock(&kernel_flag));

	}

}



#else



/*

 * Non-preemption case - just get the spinlock

 */

static inline void __lock_kernel(void)

{

	_raw_spin_lock(&kernel_flag);

}

#endif



static inline void __unlock_kernel(void)

{

	/*

	 * the BKL is not covered by lockdep, so we open-code the

	 * unlocking sequence (and thus avoid the dep-chain ops):

	 */

	_raw_spin_unlock(&kernel_flag);

	preempt_enable();

}



/*

 * Getting the big kernel lock.

 *

 * This cannot happen asynchronously, so we only need to

 * worry about other CPU's.

 */

void __lockfunc lock_kernel(void)

{

	int depth = current->lock_depth+1;

	if (likely(!depth))

		__lock_kernel();

	current->lock_depth = depth;

}



void __lockfunc unlock_kernel(void)

{

	BUG_ON(current->lock_depth < 0);

	if (likely(--current->lock_depth < 0))

		__unlock_kernel();

}



#endif



EXPORT_SYMBOL(lock_kernel);

EXPORT_SYMBOL(unlock_kernel);