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-rw-r--r--include/linux/poll.h37
-rw-r--r--include/net/sock.h2
2 files changed, 32 insertions, 7 deletions
diff --git a/include/linux/poll.h b/include/linux/poll.h
index cf40010ce0cd..48fe8bc398d1 100644
--- a/include/linux/poll.h
+++ b/include/linux/poll.h
@@ -32,21 +32,46 @@ struct poll_table_struct;
*/
typedef void (*poll_queue_proc)(struct file *, wait_queue_head_t *, struct poll_table_struct *);
+/*
+ * Do not touch the structure directly, use the access functions
+ * poll_does_not_wait() and poll_requested_events() instead.
+ */
typedef struct poll_table_struct {
- poll_queue_proc qproc;
- unsigned long key;
+ poll_queue_proc _qproc;
+ unsigned long _key;
} poll_table;
static inline void poll_wait(struct file * filp, wait_queue_head_t * wait_address, poll_table *p)
{
- if (p && wait_address)
- p->qproc(filp, wait_address, p);
+ if (p && p->_qproc && wait_address)
+ p->_qproc(filp, wait_address, p);
+}
+
+/*
+ * Return true if it is guaranteed that poll will not wait. This is the case
+ * if the poll() of another file descriptor in the set got an event, so there
+ * is no need for waiting.
+ */
+static inline bool poll_does_not_wait(const poll_table *p)
+{
+ return p == NULL || p->_qproc == NULL;
+}
+
+/*
+ * Return the set of events that the application wants to poll for.
+ * This is useful for drivers that need to know whether a DMA transfer has
+ * to be started implicitly on poll(). You typically only want to do that
+ * if the application is actually polling for POLLIN and/or POLLOUT.
+ */
+static inline unsigned long poll_requested_events(const poll_table *p)
+{
+ return p ? p->_key : ~0UL;
}
static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc)
{
- pt->qproc = qproc;
- pt->key = ~0UL; /* all events enabled */
+ pt->_qproc = qproc;
+ pt->_key = ~0UL; /* all events enabled */
}
struct poll_table_entry {
diff --git a/include/net/sock.h b/include/net/sock.h
index 04bc0b30e9e9..a6ba1f8871fd 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1854,7 +1854,7 @@ static inline bool wq_has_sleeper(struct socket_wq *wq)
static inline void sock_poll_wait(struct file *filp,
wait_queue_head_t *wait_address, poll_table *p)
{
- if (p && wait_address) {
+ if (!poll_does_not_wait(p) && wait_address) {
poll_wait(filp, wait_address, p);
/*
* We need to be sure we are in sync with the