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sched: Make migrate_disable/enable() independent of RT

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Now that the scheduler can deal with migrate disable properly, there is no
real compelling reason to make it only available for RT.

There are quite some code pathes which needlessly disable preemption in
order to prevent migration and some constructs like kmap_atomic() enforce
it implicitly.

Making it available independent of RT allows to provide a preemptible
variant of kmap_atomic() and makes the code more consistent in general.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Grudgingly-Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20201118204007.269943012@linutronix.de
This commit is contained in:
Thomas Gleixner
2020-11-18 20:48:42 +01:00
parent fa50e2b452
commit 74d862b682
6 changed files with 56 additions and 56 deletions
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38
include/linux/preempt.h
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@@ -322,7 +322,7 @@ static inline void preempt_notifier_init(struct preempt_notifier *notifier,
#endif
#if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT)
#ifdef CONFIG_SMP
/*
* Migrate-Disable and why it is undesired.
@@ -382,43 +382,11 @@ static inline void preempt_notifier_init(struct preempt_notifier *notifier,
extern void migrate_disable(void);
extern void migrate_enable(void);
#elif defined(CONFIG_PREEMPT_RT)
#else
static inline void migrate_disable(void) { }
static inline void migrate_enable(void) { }
#else /* !CONFIG_PREEMPT_RT */
/**
* migrate_disable - Prevent migration of the current task
*
* Maps to preempt_disable() which also disables preemption. Use
* migrate_disable() to annotate that the intent is to prevent migration,
* but not necessarily preemption.
*
* Can be invoked nested like preempt_disable() and needs the corresponding
* number of migrate_enable() invocations.
*/
static __always_inline void migrate_disable(void)
{
preempt_disable();
}
/**
* migrate_enable - Allow migration of the current task
*
* Counterpart to migrate_disable().
*
* As migrate_disable() can be invoked nested, only the outermost invocation
* reenables migration.
*
* Currently mapped to preempt_enable().
*/
static __always_inline void migrate_enable(void)
{
preempt_enable();
}
#endif /* CONFIG_SMP && CONFIG_PREEMPT_RT */
#endif /* CONFIG_SMP */
#endif /* __LINUX_PREEMPT_H */