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sched: remove the !PREEMPT_BKL code
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remove the !PREEMPT_BKL code.

this removes 160 lines of legacy code.

Signed-off-by: Ingo Molnar <[email protected]>
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Ingo Molnar committed Jan 25, 2008
1 parent 58b8a73 commit 6478d88
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Showing 5 changed files with 5 additions and 161 deletions.
6 changes: 1 addition & 5 deletions include/linux/hardirq.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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
#define in_atomic() ((preempt_count() & ~PREEMPT_ACTIVE) != 0)

#ifdef CONFIG_PREEMPT
# define PREEMPT_CHECK_OFFSET 1
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14 changes: 1 addition & 13 deletions include/linux/smp_lock.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
}

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4 changes: 0 additions & 4 deletions kernel/Kconfig.preempt
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Original file line number Diff line number Diff line change
Expand Up @@ -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
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19 changes: 3 additions & 16 deletions kernel/sched.c
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Original file line number Diff line number Diff line change
Expand Up @@ -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..
Expand All @@ -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);

/*
Expand All @@ -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());

Expand All @@ -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);

/*
Expand Down Expand Up @@ -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:
*/
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123 changes: 0 additions & 123 deletions lib/kernel_lock.c
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Original file line number Diff line number Diff line change
Expand Up @@ -9,7 +9,6 @@
#include <linux/module.h>
#include <linux/kallsyms.h>

#ifdef CONFIG_PREEMPT_BKL
/*
* The 'big kernel semaphore'
*
Expand Down Expand Up @@ -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);

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