Name
yield_to — 
     yield the current processor to another thread in your thread group, or accelerate that thread toward the processor it's on.
 
Synopsis
| int __sched yield_to ( | struct task_struct * p, | 
|  | bool preempt ); | 
 
Arguments
- p
- 
     target task
     
- preempt
- 
     whether task preemption is allowed or not
     
Description
   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.
Return
   true (>0) if we indeed boosted the target task.
   false (0) if we failed to boost the target.
   -ESRCH if there's no task to yield to.