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#ifndef _LITMUS_NP_H_
#define _LITMUS_NP_H_
/* Definitions related to non-preemptive sections signaled via the control
* page
*/
#ifdef CONFIG_NP_SECTION
static inline int is_kernel_np(struct task_struct *t)
{
return tsk_rt(t)->kernel_np;
}
static inline int is_user_np(struct task_struct *t)
{
return tsk_rt(t)->ctrl_page ? tsk_rt(t)->ctrl_page->sched.np.flag : 0;
}
static inline void request_exit_np(struct task_struct *t)
{
if (is_user_np(t)) {
/* Set the flag that tells user space to call
* into the kernel at the end of a critical section. */
if (likely(tsk_rt(t)->ctrl_page)) {
TRACE_TASK(t, "setting delayed_preemption flag\n");
tsk_rt(t)->ctrl_page->sched.np.preempt = 1;
}
}
}
static inline void make_np(struct task_struct *t)
{
tsk_rt(t)->kernel_np++;
}
/* Caller should check if preemption is necessary when
* the function return 0.
*/
static inline int take_np(struct task_struct *t)
{
return --tsk_rt(t)->kernel_np;
}
/* returns 0 if remote CPU needs an IPI to preempt, 1 if no IPI is required */
static inline int request_exit_np_atomic(struct task_struct *t)
{
union np_flag old, new;
if (tsk_rt(t)->ctrl_page) {
old.raw = tsk_rt(t)->ctrl_page->sched.raw;
if (old.np.flag == 0) {
/* no longer non-preemptive */
return 0;
} else if (old.np.preempt) {
/* already set, nothing for us to do */
return 1;
} else {
/* non preemptive and flag not set */
new.raw = old.raw;
new.np.preempt = 1;
/* if we get old back, then we atomically set the flag */
return cmpxchg(&tsk_rt(t)->ctrl_page->sched.raw, old.raw, new.raw) == old.raw;
/* If we raced with a concurrent change, then so be
* it. Deliver it by IPI. We don't want an unbounded
* retry loop here since tasks might exploit that to
* keep the kernel busy indefinitely. */
}
} else
return 0;
}
#else
static inline int is_kernel_np(struct task_struct* t)
{
return 0;
}
static inline int is_user_np(struct task_struct* t)
{
return 0;
}
static inline void request_exit_np(struct task_struct *t)
{
/* request_exit_np() shouldn't be called if !CONFIG_NP_SECTION */
BUG();
}
static inline int request_exit_np_atomic(struct task_struct *t)
{
return 0;
}
#endif
static inline void clear_exit_np(struct task_struct *t)
{
if (likely(tsk_rt(t)->ctrl_page))
tsk_rt(t)->ctrl_page->sched.np.preempt = 0;
}
static inline int is_np(struct task_struct *t)
{
#ifdef CONFIG_SCHED_DEBUG_TRACE
int kernel, user;
kernel = is_kernel_np(t);
user = is_user_np(t);
if (kernel || user)
TRACE_TASK(t, " is non-preemptive: kernel=%d user=%d\n",
kernel, user);
return kernel || user;
#else
return unlikely(is_kernel_np(t) || is_user_np(t));
#endif
}
#endif
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