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authorHerbert Xu <herbert@gondor.apana.org.au>2015-11-26 13:55:39 +0800
committerDavid S. Miller <davem@davemloft.net>2015-11-30 14:47:33 -0500
commit1ce0bf50ae2233c7115a18c0c623662d177b434c (patch)
tree41860e17fe4b2184055d29e669e503d09796775a /include/linux/wait.h
parentc52fd05a2ff2ad20e2a7056baf314c7d1d624ba9 (diff)
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net: Generalise wq_has_sleeper helper
The memory barrier in the helper wq_has_sleeper is needed by just about every user of waitqueue_active. This patch generalises it by making it take a wait_queue_head_t directly. The existing helper is renamed to skwq_has_sleeper. Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/wait.h')
-rw-r--r--include/linux/wait.h21
1 files changed, 21 insertions, 0 deletions
diff --git a/include/linux/wait.h b/include/linux/wait.h
index 1e1bf9f..6aa09a8 100644
--- a/include/linux/wait.h
+++ b/include/linux/wait.h
@@ -107,6 +107,27 @@ static inline int waitqueue_active(wait_queue_head_t *q)
return !list_empty(&q->task_list);
}
+/**
+ * wq_has_sleeper - check if there are any waiting processes
+ * @wq: wait queue head
+ *
+ * Returns true if wq has waiting processes
+ *
+ * Please refer to the comment for waitqueue_active.
+ */
+static inline bool wq_has_sleeper(wait_queue_head_t *wq)
+{
+ /*
+ * We need to be sure we are in sync with the
+ * add_wait_queue modifications to the wait queue.
+ *
+ * This memory barrier should be paired with one on the
+ * waiting side.
+ */
+ smp_mb();
+ return waitqueue_active(wq);
+}
+
extern void add_wait_queue(wait_queue_head_t *q, wait_queue_t *wait);
extern void add_wait_queue_exclusive(wait_queue_head_t *q, wait_queue_t *wait);
extern void remove_wait_queue(wait_queue_head_t *q, wait_queue_t *wait);
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