Merge branch 'fixes' into next/fixes-non-critical

Merge a set of fixes that we missed sending in before v4.0 release. These
will also be sent to -stable.

* fixes: (659 commits)
  ARM: at91/dt: sama5d3 xplained: add phy address for macb1
  kbuild: Create directory for target DTB
  ARM: mvebu: Disable CPU Idle on Armada 38x
  arm64: juno: Fix misleading name of UART reference clock
  ARM: dts: sunxi: Remove overclocked/overvoltaged OPP
  ARM: dts: sun4i: a10-lime: Override and remove 1008MHz OPP setting
  ARM: socfpga: dts: fix spi1 interrupt
  ARM: dts: Fix gpio interrupts for dm816x
  ARM: dts: dra7: remove ti,hwmod property from pcie phy
  ARM: EXYNOS: Fix build breakage cpuidle on !SMP
  ARM: OMAP: dmtimer: disable pm runtime on remove
  ARM: OMAP: dmtimer: check for pm_runtime_get_sync() failure
  ARM: dts: fix lid and power pin-functions for exynos5250-spring
  ARM: dts: fix mmc node updates for exynos5250-spring
  ARM: OMAP2+: Fix socbus family info for AM33xx devices
  ARM: dts: omap3: Add missing dmas for crypto
  + 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;
 }