diff options
author | Thomas Gleixner <tglx@linutronix.de> | 2011-12-12 12:29:04 +0100 |
---|---|---|
committer | Clark Williams <williams@redhat.com> | 2012-02-15 10:33:03 -0600 |
commit | c8e451704e219731d67bfd66ce15fca9952124e9 (patch) | |
tree | 98bd15b8770e22b6e6c811a4aba37ade357378b4 /kernel | |
parent | bbcfa4c185c14c6446fa22201c372a7325ce968a (diff) |
wait-simple: Simple waitqueue implementation
wait_queue is a swiss army knife and in most of the cases the
complexity is not needed. For RT waitqueues are a constant source of
trouble as we can't convert the head lock to a raw spinlock due to
fancy and long lasting callbacks.
Provide a slim version, which allows RT to replace wait queues. This
should go mainline as well, as it lowers memory consumption and
runtime overhead.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel')
-rw-r--r-- | kernel/Makefile | 2 | ||||
-rw-r--r-- | kernel/wait-simple.c | 63 |
2 files changed, 64 insertions, 1 deletions
diff --git a/kernel/Makefile b/kernel/Makefile index c961d3abfe4c..ae86e48cdaff 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -10,7 +10,7 @@ obj-y = sched.o fork.o exec_domain.o panic.o printk.o \ kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o \ hrtimer.o nsproxy.o srcu.o semaphore.o \ notifier.o ksysfs.o sched_clock.o cred.o \ - async.o range.o + async.o range.o wait-simple.o obj-y += groups.o ifdef CONFIG_FUNCTION_TRACER diff --git a/kernel/wait-simple.c b/kernel/wait-simple.c new file mode 100644 index 000000000000..9e53eaaa4b68 --- /dev/null +++ b/kernel/wait-simple.c @@ -0,0 +1,63 @@ +/* + * Simple waitqueues without fancy flags and callbacks + * + * (C) 2011 Thomas Gleixner <tglx@linutronix.de> + * + * Based on kernel/wait.c + * + * For licencing details see kernel-base/COPYING + */ +#include <linux/init.h> +#include <linux/export.h> +#include <linux/sched.h> +#include <linux/wait-simple.h> + +void __init_swait_head(struct swait_head *head, struct lock_class_key *key) +{ + raw_spin_lock_init(&head->lock); + lockdep_set_class(&head->lock, key); + INIT_LIST_HEAD(&head->list); +} +EXPORT_SYMBOL_GPL(__init_swait_head); + +void swait_prepare(struct swait_head *head, struct swaiter *w, int state) +{ + unsigned long flags; + + raw_spin_lock_irqsave(&head->lock, flags); + w->task = current; + __swait_enqueue(head, w); + set_current_state(state); + raw_spin_unlock_irqrestore(&head->lock, flags); +} +EXPORT_SYMBOL_GPL(swait_prepare); + +void swait_finish(struct swait_head *head, struct swaiter *w) +{ + unsigned long flags; + + __set_current_state(TASK_RUNNING); + if (w->task) { + raw_spin_lock_irqsave(&head->lock, flags); + __swait_dequeue(w); + raw_spin_unlock_irqrestore(&head->lock, flags); + } +} +EXPORT_SYMBOL_GPL(swait_finish); + +void __swait_wake(struct swait_head *head, unsigned int state) +{ + struct swaiter *curr, *next; + unsigned long flags; + + raw_spin_lock_irqsave(&head->lock, flags); + + list_for_each_entry_safe(curr, next, &head->list, node) { + if (wake_up_state(curr->task, state)) { + __swait_dequeue(curr); + curr->task = NULL; + } + } + + raw_spin_unlock_irqrestore(&head->lock, flags); +} |