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authorThomas Gleixner <tglx@linutronix.de>2017-03-09 12:06:41 +0100
committerThomas Gleixner <tglx@linutronix.de>2017-03-09 12:06:41 +0100
commit920c634aff6cb66e7f352668521eb1313897e93c (patch)
tree0f2e2eb15756fdd93c8ea47f9080fc3c1abeeae6 /include/linux/sched/wake_q.h
parentb28ace12661fbcfd90959c1e84ff5a85113a82a1 (diff)
parent4b9de5da7e120c7f02395da729f0ec77ce7a6044 (diff)
Merge tag 'irq-fixes-4.11-rc2' of git://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms into irq/urgent
Pull irqchip/irqdomain updates for 4.11-rc2 from Marc Zyngier - irqchip/crossbar: Some type tidying up - irqchip/gicv3-its: Workaround for a Qualcomm erratum - irqdomain: Compile for for systems that don't use CONFIG_IRQ_DOMAIN Fixed up minor conflict in the crossbar driver.
Diffstat (limited to 'include/linux/sched/wake_q.h')
-rw-r--r--include/linux/sched/wake_q.h53
1 files changed, 53 insertions, 0 deletions
diff --git a/include/linux/sched/wake_q.h b/include/linux/sched/wake_q.h
new file mode 100644
index 000000000000..d03d8a9047dc
--- /dev/null
+++ b/include/linux/sched/wake_q.h
@@ -0,0 +1,53 @@
+#ifndef _LINUX_SCHED_WAKE_Q_H
+#define _LINUX_SCHED_WAKE_Q_H
+
+/*
+ * Wake-queues are lists of tasks with a pending wakeup, whose
+ * callers have already marked the task as woken internally,
+ * and can thus carry on. A common use case is being able to
+ * do the wakeups once the corresponding user lock as been
+ * released.
+ *
+ * We hold reference to each task in the list across the wakeup,
+ * thus guaranteeing that the memory is still valid by the time
+ * the actual wakeups are performed in wake_up_q().
+ *
+ * One per task suffices, because there's never a need for a task to be
+ * in two wake queues simultaneously; it is forbidden to abandon a task
+ * in a wake queue (a call to wake_up_q() _must_ follow), so if a task is
+ * already in a wake queue, the wakeup will happen soon and the second
+ * waker can just skip it.
+ *
+ * The DEFINE_WAKE_Q macro declares and initializes the list head.
+ * wake_up_q() does NOT reinitialize the list; it's expected to be
+ * called near the end of a function. Otherwise, the list can be
+ * re-initialized for later re-use by wake_q_init().
+ *
+ * Note that this can cause spurious wakeups. schedule() callers
+ * must ensure the call is done inside a loop, confirming that the
+ * wakeup condition has in fact occurred.
+ */
+
+#include <linux/sched.h>
+
+struct wake_q_head {
+ struct wake_q_node *first;
+ struct wake_q_node **lastp;
+};
+
+#define WAKE_Q_TAIL ((struct wake_q_node *) 0x01)
+
+#define DEFINE_WAKE_Q(name) \
+ struct wake_q_head name = { WAKE_Q_TAIL, &name.first }
+
+static inline void wake_q_init(struct wake_q_head *head)
+{
+ head->first = WAKE_Q_TAIL;
+ head->lastp = &head->first;
+}
+
+extern void wake_q_add(struct wake_q_head *head,
+ struct task_struct *task);
+extern void wake_up_q(struct wake_q_head *head);
+
+#endif /* _LINUX_SCHED_WAKE_Q_H */