Merge tag 'omap-for-v4.1/wl12xx-dt' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap into next/dt

Merge "wireless wl12xx and omap device tree changes for v4.1" from Tony
Lindgren:

Wireless and omap changes to make wl12xx driver to use device tree
data instead of platform data from Eliad Peller <eliad@wizery.com>:

- Add device-tree support to the wlcore (wl12xx/wl18xx) driver.

- Update the current users to use the bindings instead of pdata-quirks.

- Finally, remove the deprecated wl12xx_platform_data struct

Note that da850 board file code that still uses the platform data,
but we have da850.dtsi that can be used instead. So it was decided
that we should try to remove the wl12xx support from the da850
board file as suggested by Sekhar Nori <nsekhar@ti.com>. As it's
the last patch in the series, the last patch can be simply reverted
if needed.

As this series touches quite a bit of arch code, it was suggested
by Kalle Valo <kvalo@codeaurora.org> that the whole series should
be merged via the arm-soc tree.

* tag 'omap-for-v4.1/wl12xx-dt' of git://git.kernel.org/pub/scm/linux/kernel/git/tmlind/linux-omap:
  wlcore: remove wl12xx_platform_data
  ARM: dts: add wl12xx/wl18xx bindings
  wlcore: add device-tree support
  dt: bindings: add TI's wilink wireless device
  wl12xx: use frequency instead of enumerations for pdata clocks
  wlcore: set irq_trigger in board files instead of hiding behind a quirk
  + Linux 4.0-rc4

Signed-off-by: Olof Johansson <olof@lixom.net>

1 files changed, 52 insertions, 4 deletions

diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index f28849394791..41ff75b478c6 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -2728,19 +2728,57 @@ bool flush_work(struct work_struct *work)
 }
 EXPORT_SYMBOL_GPL(flush_work);
 
+struct cwt_wait {
+	wait_queue_t		wait;
+	struct work_struct	*work;
+};
+
+static int cwt_wakefn(wait_queue_t *wait, unsigned mode, int sync, void *key)
+{
+	struct cwt_wait *cwait = container_of(wait, struct cwt_wait, wait);
+
+	if (cwait->work != key)
+		return 0;
+	return autoremove_wake_function(wait, mode, sync, key);
+}
+
 static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
 {
+	static DECLARE_WAIT_QUEUE_HEAD(cancel_waitq);
 	unsigned long flags;
 	int ret;
 
 	do {
 		ret = try_to_grab_pending(work, is_dwork, &flags);
 		/*
-		 * If someone else is canceling, wait for the same event it
-		 * would be waiting for before retrying.
+		 * If someone else is already canceling, wait for it to
+		 * finish.  flush_work() doesn't work for PREEMPT_NONE
+		 * because we may get scheduled between @work's completion
+		 * and the other canceling task resuming and clearing
+		 * CANCELING - flush_work() will return false immediately
+		 * as @work is no longer busy, try_to_grab_pending() will
+		 * return -ENOENT as @work is still being canceled and the
+		 * other canceling task won't be able to clear CANCELING as
+		 * we're hogging the CPU.
+		 *
+		 * Let's wait for completion using a waitqueue.  As this
+		 * may lead to the thundering herd problem, use a custom
+		 * wake function which matches @work along with exclusive
+		 * wait and wakeup.
 		 */
-		if (unlikely(ret == -ENOENT))
-			flush_work(work);
+		if (unlikely(ret == -ENOENT)) {
+			struct cwt_wait cwait;
+
+			init_wait(&cwait.wait);
+			cwait.wait.func = cwt_wakefn;
+			cwait.work = work;
+
+			prepare_to_wait_exclusive(&cancel_waitq, &cwait.wait,
+						  TASK_UNINTERRUPTIBLE);
+			if (work_is_canceling(work))
+				schedule();
+			finish_wait(&cancel_waitq, &cwait.wait);
+		}
 	} while (unlikely(ret < 0));
 
 	/* tell other tasks trying to grab @work to back off */
@@ -2749,6 +2787,16 @@ static bool __cancel_work_timer(struct work_struct *work, bool is_dwork)
 
 	flush_work(work);
 	clear_work_data(work);
+
+	/*
+	 * Paired with prepare_to_wait() above so that either
+	 * waitqueue_active() is visible here or !work_is_canceling() is
+	 * visible there.
+	 */
+	smp_mb();
+	if (waitqueue_active(&cancel_waitq))
+		__wake_up(&cancel_waitq, TASK_NORMAL, 1, work);
+
 	return ret;
 }