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authorDavid Howells <dhowells@redhat.com>2019-09-24 16:07:45 +0100
committerDavid Howells <dhowells@redhat.com>2019-10-31 15:12:23 +0000
commitf94df9890e98f2090c6a8d70c795134863b70201 (patch)
treeb8af2f2af5a1368a200d26002d61c6c2e59b7c1c /kernel/sched
parentce4dd4429b3c7e4506870796f3b8b06d707d2928 (diff)
Add wake_up_interruptible_sync_poll_locked()
Add a wakeup call for a case whereby the caller already has the waitqueue spinlock held. This can be used by pipes to alter the ring buffer indices and issue a wakeup under the same spinlock. Signed-off-by: David Howells <dhowells@redhat.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/wait.c23
1 files changed, 23 insertions, 0 deletions
diff --git a/kernel/sched/wait.c b/kernel/sched/wait.c
index b4b52361dab7..ba059fbfc53a 100644
--- a/kernel/sched/wait.c
+++ b/kernel/sched/wait.c
@@ -191,6 +191,29 @@ void __wake_up_sync_key(struct wait_queue_head *wq_head, unsigned int mode,
}
EXPORT_SYMBOL_GPL(__wake_up_sync_key);
+/**
+ * __wake_up_locked_sync_key - wake up a thread blocked on a locked waitqueue.
+ * @wq_head: the waitqueue
+ * @mode: which threads
+ * @key: opaque value to be passed to wakeup targets
+ *
+ * The sync wakeup differs in that the waker knows that it will schedule
+ * away soon, so while the target thread will be woken up, it will not
+ * be migrated to another CPU - ie. the two threads are 'synchronized'
+ * with each other. This can prevent needless bouncing between CPUs.
+ *
+ * On UP it can prevent extra preemption.
+ *
+ * If this function wakes up a task, it executes a full memory barrier before
+ * accessing the task state.
+ */
+void __wake_up_locked_sync_key(struct wait_queue_head *wq_head,
+ unsigned int mode, void *key)
+{
+ __wake_up_common(wq_head, mode, 1, WF_SYNC, key, NULL);
+}
+EXPORT_SYMBOL_GPL(__wake_up_locked_sync_key);
+
/*
* __wake_up_sync - see __wake_up_sync_key()
*/