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sched: Create more preempt_count accessors 

We need a few special preempt_count accessors:
 - task_preempt_count() for when we're interested in the preemption
   count of another (non-running) task.
 - init_task_preempt_count() for properly initializing the preemption
   count.
 - init_idle_preempt_count() a special case of the above for the idle
   threads.

With these no generic code ever touches thread_info::preempt_count
anymore and architectures could choose to remove it.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-jf5swrio8l78j37d06fzmo4r@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Peter Zijlstra 2013-08-14 14:55:46 +02:00 committed by Ingo Molnar
parent a787870924
commit 0102874755
3 changed files with 18 additions and 5 deletions
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14
include/asm-generic/preempt.h
View File

@ -27,6 +27,20 @@ static __always_inline void preempt_count_set(int pc)
*preempt_count_ptr() = pc;
}
/*
* must be macros to avoid header recursion hell
*/
#define task_preempt_count(p) \
(task_thread_info(p)->preempt_count & ~PREEMPT_NEED_RESCHED)
#define init_task_preempt_count(p) do { \
task_thread_info(p)->preempt_count = PREEMPT_DISABLED; \
} while (0)
#define init_idle_preempt_count(p, cpu) do { \
task_thread_info(p)->preempt_count = PREEMPT_ENABLED; \
} while (0)
/*
* We fold the NEED_RESCHED bit into the preempt count such that
* preempt_enable() can decrement and test for needing to reschedule with a

2
include/trace/events/sched.h
View File

@ -100,7 +100,7 @@ static inline long __trace_sched_switch_state(struct task_struct *p)
/*
* For all intents and purposes a preempted task is a running task.
*/
if (task_thread_info(p)->preempt_count & PREEMPT_ACTIVE)
if (task_preempt_count(p) & PREEMPT_ACTIVE)
state = TASK_RUNNING | TASK_STATE_MAX;
#endif

7
kernel/sched/core.c
View File

@ -983,7 +983,7 @@ void set_task_cpu(struct task_struct *p, unsigned int new_cpu)
* ttwu() will sort out the placement.
*/
WARN_ON_ONCE(p->state != TASK_RUNNING && p->state != TASK_WAKING &&
!(task_thread_info(p)->preempt_count & PREEMPT_ACTIVE));
!(task_preempt_count(p) & PREEMPT_ACTIVE));
#ifdef CONFIG_LOCKDEP
/*
@ -1723,8 +1723,7 @@ void sched_fork(struct task_struct *p)
p->on_cpu = 0;
#endif
#ifdef CONFIG_PREEMPT_COUNT
/* Want to start with kernel preemption disabled. */
task_thread_info(p)->preempt_count = PREEMPT_DISABLED;
init_task_preempt_count(p);
#endif
#ifdef CONFIG_SMP
plist_node_init(&p->pushable_tasks, MAX_PRIO);
@ -4217,7 +4216,7 @@ void init_idle(struct task_struct *idle, int cpu)
raw_spin_unlock_irqrestore(&rq->lock, flags);
/* Set the preempt count _outside_ the spinlocks! */
task_thread_info(idle)->preempt_count = PREEMPT_ENABLED;
init_idle_preempt_count(idle, cpu);
/*
* The idle tasks have their own, simple scheduling class: