rq_unlock(rq, &rf);
}
+/*
+ * Invoked from try_to_wake_up() to check whether the task can be woken up.
+ *
+ * The caller holds p::pi_lock if p != current or has preemption
+ * disabled when p == current.
+ *
+ * The rules of PREEMPT_RT saved_state:
+ *
+ * The related locking code always holds p::pi_lock when updating
+ * p::saved_state, which means the code is fully serialized in both cases.
+ *
+ * The lock wait and lock wakeups happen via TASK_RTLOCK_WAIT. No other
+ * bits set. This allows to distinguish all wakeup scenarios.
+ */
+static __always_inline
+bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success)
+{
+ if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)) {
+ WARN_ON_ONCE((state & TASK_RTLOCK_WAIT) &&
+ state != TASK_RTLOCK_WAIT);
+ }
+
+ if (READ_ONCE(p->__state) & state) {
+ *success = 1;
+ return true;
+ }
+
+#ifdef CONFIG_PREEMPT_RT
+ /*
+ * Saved state preserves the task state across blocking on
+ * an RT lock. If the state matches, set p::saved_state to
+ * TASK_RUNNING, but do not wake the task because it waits
+ * for a lock wakeup. Also indicate success because from
+ * the regular waker's point of view this has succeeded.
+ *
+ * After acquiring the lock the task will restore p::__state
+ * from p::saved_state which ensures that the regular
+ * wakeup is not lost. The restore will also set
+ * p::saved_state to TASK_RUNNING so any further tests will
+ * not result in false positives vs. @success
+ */
+ if (p->saved_state & state) {
+ p->saved_state = TASK_RUNNING;
+ *success = 1;
+ }
+#endif
+ return false;
+}
+
/*
* Notes on Program-Order guarantees on SMP systems.
*
* - we're serialized against set_special_state() by virtue of
* it disabling IRQs (this allows not taking ->pi_lock).
*/
- if (!(READ_ONCE(p->__state) & state))
+ if (!ttwu_state_match(p, state, &success))
goto out;
- success = 1;
trace_sched_waking(p);
WRITE_ONCE(p->__state, TASK_RUNNING);
trace_sched_wakeup(p);
*/
raw_spin_lock_irqsave(&p->pi_lock, flags);
smp_mb__after_spinlock();
- if (!(READ_ONCE(p->__state) & state))
+ if (!ttwu_state_match(p, state, &success))
goto unlock;
trace_sched_waking(p);
- /* We're going to change ->state: */
- success = 1;
-
/*
* Ensure we load p->on_rq _after_ p->state, otherwise it would
* be possible to, falsely, observe p->on_rq == 0 and get stuck
#endif /* CONFIG_SCHED_CORE */
+/*
+ * Constants for the sched_mode argument of __schedule().
+ *
+ * The mode argument allows RT enabled kernels to differentiate a
+ * preemption from blocking on an 'sleeping' spin/rwlock. Note that
+ * SM_MASK_PREEMPT for !RT has all bits set, which allows the compiler to
+ * optimize the AND operation out and just check for zero.
+ */
+#define SM_NONE 0x0
+#define SM_PREEMPT 0x1
+#define SM_RTLOCK_WAIT 0x2
+
+#ifndef CONFIG_PREEMPT_RT
+# define SM_MASK_PREEMPT (~0U)
+#else
+# define SM_MASK_PREEMPT SM_PREEMPT
+#endif
+
/*
* __schedule() is the main scheduler function.
*
*
* WARNING: must be called with preemption disabled!
*/
-static void __sched notrace __schedule(bool preempt)
+static void __sched notrace __schedule(unsigned int sched_mode)
{
struct task_struct *prev, *next;
unsigned long *switch_count;
rq = cpu_rq(cpu);
prev = rq->curr;
- schedule_debug(prev, preempt);
+ schedule_debug(prev, !!sched_mode);
if (sched_feat(HRTICK) || sched_feat(HRTICK_DL))
hrtick_clear(rq);
local_irq_disable();
- rcu_note_context_switch(preempt);
+ rcu_note_context_switch(!!sched_mode);
/*
* Make sure that signal_pending_state()->signal_pending() below
* - ptrace_{,un}freeze_traced() can change ->state underneath us.
*/
prev_state = READ_ONCE(prev->__state);
- if (!preempt && prev_state) {
+ if (!(sched_mode & SM_MASK_PREEMPT) && prev_state) {
if (signal_pending_state(prev_state, prev)) {
WRITE_ONCE(prev->__state, TASK_RUNNING);
} else {
migrate_disable_switch(rq, prev);
psi_sched_switch(prev, next, !task_on_rq_queued(prev));
- trace_sched_switch(preempt, prev, next);
+ trace_sched_switch(sched_mode & SM_MASK_PREEMPT, prev, next);
/* Also unlocks the rq: */
rq = context_switch(rq, prev, next, &rf);
/* Tell freezer to ignore us: */
current->flags |= PF_NOFREEZE;
- __schedule(false);
+ __schedule(SM_NONE);
BUG();
/* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */
sched_submit_work(tsk);
do {
preempt_disable();
- __schedule(false);
+ __schedule(SM_NONE);
sched_preempt_enable_no_resched();
} while (need_resched());
sched_update_worker(tsk);
*/
WARN_ON_ONCE(current->__state);
do {
- __schedule(false);
+ __schedule(SM_NONE);
} while (need_resched());
}
preempt_disable();
}
+#ifdef CONFIG_PREEMPT_RT
+void __sched notrace schedule_rtlock(void)
+{
+ do {
+ preempt_disable();
+ __schedule(SM_RTLOCK_WAIT);
+ sched_preempt_enable_no_resched();
+ } while (need_resched());
+}
+NOKPROBE_SYMBOL(schedule_rtlock);
+#endif
+
static void __sched notrace preempt_schedule_common(void)
{
do {
*/
preempt_disable_notrace();
preempt_latency_start(1);
- __schedule(true);
+ __schedule(SM_PREEMPT);
preempt_latency_stop(1);
preempt_enable_no_resched_notrace();
* an infinite recursion.
*/
prev_ctx = exception_enter();
- __schedule(true);
+ __schedule(SM_PREEMPT);
exception_exit(prev_ctx);
preempt_latency_stop(1);
do {
preempt_disable();
local_irq_enable();
- __schedule(true);
+ __schedule(SM_PREEMPT);
local_irq_disable();
sched_preempt_enable_no_resched();
} while (need_resched());
projects / linux-2.6-microblaze.git / blobdiff