diff --git a/fs/eventpoll.c b/fs/eventpoll.c
index 4d9d3a4..ca30007 100644
--- a/fs/eventpoll.c
+++ b/fs/eventpoll.c
@@ -699,9 +699,12 @@
 			       void *priv)
 {
 	struct epitem *epi, *tmp;
+	poll_table pt;
 
+	init_poll_funcptr(&pt, NULL);
 	list_for_each_entry_safe(epi, tmp, head, rdllink) {
-		if (epi->ffd.file->f_op->poll(epi->ffd.file, NULL) &
+		pt._key = epi->event.events;
+		if (epi->ffd.file->f_op->poll(epi->ffd.file, &pt) &
 		    epi->event.events)
 			return POLLIN | POLLRDNORM;
 		else {
@@ -1097,6 +1100,7 @@
 	/* Initialize the poll table using the queue callback */
 	epq.epi = epi;
 	init_poll_funcptr(&epq.pt, ep_ptable_queue_proc);
+	epq.pt._key = event->events;
 
 	/*
 	 * Attach the item to the poll hooks and get current event bits.
@@ -1191,6 +1195,9 @@
 {
 	int pwake = 0;
 	unsigned int revents;
+	poll_table pt;
+
+	init_poll_funcptr(&pt, NULL);
 
 	/*
 	 * Set the new event interest mask before calling f_op->poll();
@@ -1198,13 +1205,14 @@
 	 * f_op->poll() call and the new event set registering.
 	 */
 	epi->event.events = event->events;
+	pt._key = event->events;
 	epi->event.data = event->data; /* protected by mtx */
 
 	/*
 	 * Get current event bits. We can safely use the file* here because
 	 * its usage count has been increased by the caller of this function.
 	 */
-	revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL);
+	revents = epi->ffd.file->f_op->poll(epi->ffd.file, &pt);
 
 	/*
 	 * If the item is "hot" and it is not registered inside the ready
@@ -1239,6 +1247,9 @@
 	unsigned int revents;
 	struct epitem *epi;
 	struct epoll_event __user *uevent;
+	poll_table pt;
+
+	init_poll_funcptr(&pt, NULL);
 
 	/*
 	 * We can loop without lock because we are passed a task private list.
@@ -1251,7 +1262,8 @@
 
 		list_del_init(&epi->rdllink);
 
-		revents = epi->ffd.file->f_op->poll(epi->ffd.file, NULL) &
+		pt._key = epi->event.events;
+		revents = epi->ffd.file->f_op->poll(epi->ffd.file, &pt) &
 			epi->event.events;
 
 		/*
diff --git a/fs/select.c b/fs/select.c
index e782258..ecfd0b1 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -223,7 +223,7 @@
 	get_file(filp);
 	entry->filp = filp;
 	entry->wait_address = wait_address;
-	entry->key = p->key;
+	entry->key = p->_key;
 	init_waitqueue_func_entry(&entry->wait, pollwake);
 	entry->wait.private = pwq;
 	add_wait_queue(wait_address, &entry->wait);
@@ -386,13 +386,11 @@
 static inline void wait_key_set(poll_table *wait, unsigned long in,
 				unsigned long out, unsigned long bit)
 {
-	if (wait) {
-		wait->key = POLLEX_SET;
-		if (in & bit)
-			wait->key |= POLLIN_SET;
-		if (out & bit)
-			wait->key |= POLLOUT_SET;
-	}
+	wait->_key = POLLEX_SET;
+	if (in & bit)
+		wait->_key |= POLLIN_SET;
+	if (out & bit)
+		wait->_key |= POLLOUT_SET;
 }
 
 int do_select(int n, fd_set_bits *fds, struct timespec *end_time)
@@ -414,7 +412,7 @@
 	poll_initwait(&table);
 	wait = &table.pt;
 	if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
-		wait = NULL;
+		wait->_qproc = NULL;
 		timed_out = 1;
 	}
 
@@ -459,17 +457,17 @@
 					if ((mask & POLLIN_SET) && (in & bit)) {
 						res_in |= bit;
 						retval++;
-						wait = NULL;
+						wait->_qproc = NULL;
 					}
 					if ((mask & POLLOUT_SET) && (out & bit)) {
 						res_out |= bit;
 						retval++;
-						wait = NULL;
+						wait->_qproc = NULL;
 					}
 					if ((mask & POLLEX_SET) && (ex & bit)) {
 						res_ex |= bit;
 						retval++;
-						wait = NULL;
+						wait->_qproc = NULL;
 					}
 				}
 			}
@@ -481,7 +479,7 @@
 				*rexp = res_ex;
 			cond_resched();
 		}
-		wait = NULL;
+		wait->_qproc = NULL;
 		if (retval || timed_out || signal_pending(current))
 			break;
 		if (table.error) {
@@ -720,7 +718,7 @@
  * interested in events matching the pollfd->events mask, and the result
  * matching that mask is both recorded in pollfd->revents and returned. The
  * pwait poll_table will be used by the fd-provided poll handler for waiting,
- * if non-NULL.
+ * if pwait->_qproc is non-NULL.
  */
 static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait)
 {
@@ -738,9 +736,7 @@
 		if (file != NULL) {
 			mask = DEFAULT_POLLMASK;
 			if (file->f_op && file->f_op->poll) {
-				if (pwait)
-					pwait->key = pollfd->events |
-							POLLERR | POLLHUP;
+				pwait->_key = pollfd->events|POLLERR|POLLHUP;
 				mask = file->f_op->poll(file, pwait);
 			}
 			/* Mask out unneeded events. */
@@ -763,7 +759,7 @@
 
 	/* Optimise the no-wait case */
 	if (end_time && !end_time->tv_sec && !end_time->tv_nsec) {
-		pt = NULL;
+		pt->_qproc = NULL;
 		timed_out = 1;
 	}
 
@@ -781,22 +777,22 @@
 			for (; pfd != pfd_end; pfd++) {
 				/*
 				 * Fish for events. If we found one, record it
-				 * and kill the poll_table, so we don't
+				 * and kill poll_table->_qproc, so we don't
 				 * needlessly register any other waiters after
 				 * this. They'll get immediately deregistered
 				 * when we break out and return.
 				 */
 				if (do_pollfd(pfd, pt)) {
 					count++;
-					pt = NULL;
+					pt->_qproc = NULL;
 				}
 			}
 		}
 		/*
 		 * All waiters have already been registered, so don't provide
-		 * a poll_table to them on the next loop iteration.
+		 * a poll_table->_qproc to them on the next loop iteration.
 		 */
-		pt = NULL;
+		pt->_qproc = NULL;
 		if (!count) {
 			count = wait->error;
 			if (signal_pending(current))
diff --git a/include/linux/poll.h b/include/linux/poll.h
index cf40010..48fe8bc 100644
--- a/include/linux/poll.h
+++ b/include/linux/poll.h
@@ -32,21 +32,46 @@
  */
 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 04bc0b3..a6ba1f8 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1854,7 +1854,7 @@
 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
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index eb4277c..d510353 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -2206,7 +2206,7 @@
 	}
 
 	/* No write status requested, avoid expensive OUT tests. */
-	if (wait && !(wait->key & (POLLWRBAND | POLLWRNORM | POLLOUT)))
+	if (!(poll_requested_events(wait) & (POLLWRBAND|POLLWRNORM|POLLOUT)))
 		return mask;
 
 	writable = unix_writable(sk);