[wait_queue] Method to peek the wait queue head
Adds a method to peek the thread that is at the head of the wait queue.
Updates the C++ WaitQueue wrapper and brings back some previously removed wrappers.
Test: Still compiles. No functional changes.
Change-Id: I5244c13bc1ef7ae53c23d27bb3cc5977d9fbd990
diff --git a/kernel/include/kernel/wait.h b/kernel/include/kernel/wait.h
index fbe9339..2b25e58 100644
--- a/kernel/include/kernel/wait.h
+++ b/kernel/include/kernel/wait.h
@@ -62,6 +62,10 @@
int wait_queue_blocked_priority(wait_queue_t*) TA_REQ(thread_lock);
+// returns the current highest priority blocked thread on this wait queue, or
+// null if no threads are blocked.
+struct thread* wait_queue_peek(wait_queue_t*) TA_REQ(thread_lock);
+
// release one or more threads from the wait queue.
// reschedule = should the system reschedule if any is released.
// wait_queue_error = what wait_queue_block() should return for the blocking thread.
@@ -105,10 +109,21 @@
return wait_queue_block(&wq_, deadline);
}
+ struct thread* Peek() TA_REQ(thread_lock) {
+ return wait_queue_peek(&wq_);
+ }
+
int WakeOne(bool reschedule, zx_status_t wait_queue_error) TA_REQ(thread_lock) {
return wait_queue_wake_one(&wq_, reschedule, wait_queue_error);
}
+ bool IsEmpty() TA_REQ(thread_lock) { return wait_queue_is_empty(&wq_); }
+
+ static zx_status_t UnblockThread(struct thread* t, zx_status_t wait_queue_error)
+ TA_REQ(thread_lock) {
+ return wait_queue_unblock_thread(t, wait_queue_error);
+ }
+
private:
wait_queue_t wq_ = WAIT_QUEUE_INITIAL_VALUE(wq_);
};
diff --git a/kernel/kernel/wait.cpp b/kernel/kernel/wait.cpp
index f147908..5095929 100644
--- a/kernel/kernel/wait.cpp
+++ b/kernel/kernel/wait.cpp
@@ -176,6 +176,11 @@
return t->effec_priority;
}
+// returns a reference to the highest priority thread queued
+thread_t* wait_queue_peek(wait_queue_t* wait) {
+ return list_peek_head_type(&wait->heads, thread_t, wait_queue_heads_node);
+}
+
static void wait_queue_timeout_handler(timer_t* timer, zx_time_t now,
void* arg) {
thread_t* thread = (thread_t*)arg;
