From: Mike Galbraith <efault@gmx.de>
Add a yield_to function to the scheduler code, allowing us to
give enough of our timeslice to another thread to allow it to
run and release whatever resource we need it to release.
We may want to use this to provide a sys_yield_to system call
one day.
Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Not-signed-off-by: Mike Galbraith <efault@gmx.de>
---
Mike, want to change the above into a Signed-off-by: ? :)
This code seems to work well.
diff --git a/include/linux/sched.h b/include/linux/sched.h
index c5f926c..0b8a3e6 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1083,6 +1083,7 @@ struct sched_class {
void (*enqueue_task) (struct rq *rq, struct task_struct *p, int wakeup);
void (*dequeue_task) (struct rq *rq, struct task_struct *p, int sleep);
void (*yield_task) (struct rq *rq);
+ int (*yield_to_task) (struct task_struct *p, int preempt);
void (*check_preempt_curr) (struct rq *rq, struct task_struct *p, int flags);
@@ -1981,6 +1982,7 @@ static inline int rt_mutex_getprio(struct task_struct *p)
# define rt_mutex_adjust_pi(p) do { } while (0)
#endif
+extern void yield_to(struct task_struct *p, int preempt);
extern void set_user_nice(struct task_struct *p, long nice);
extern int task_prio(const struct task_struct *p);
extern int task_nice(const struct task_struct *p);
diff --git a/kernel/sched.c b/kernel/sched.c
index f8e5a25..ffa7a9d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -6901,6 +6901,53 @@ void __sched yield(void)
}
EXPORT_SYMBOL(yield);
+/**
+ * yield_to - yield the current processor to another thread in
+ * your thread group, or accelerate that thread toward the
+ * processor it's on.
+ *
+ * It's the caller's job to ensure that the target task struct
+ * can't go away on us before we can do any checks.
+ */
+void __sched yield_to(struct task_struct *p, int preempt)
+{
+ struct task_struct *curr = ...
