[3.8.y.z extended stable] Patch "rapidio/tsi721: fix tasklet termination in dma channel release" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    rapidio/tsi721: fix tasklet termination in dma channel release

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.21.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From d42c8b9010ee1abf6c178f472ed858375d408b6f Mon Sep 17 00:00:00 2001
From: Alexandre Bounine <alexandre.bounine at idt.com>
Date: Mon, 3 Mar 2014 15:38:36 -0800
Subject: rapidio/tsi721: fix tasklet termination in dma channel release

commit 04379dffdd4da820d51a1566ad2e86f3b1ad97ed upstream.

This patch is a modification of the patch originally proposed by
Xiaotian Feng <xtfeng at gmail.com>: https://lkml.org/lkml/2012/11/5/413
This new version disables DMA channel interrupts and ensures that the
tasklet wil not be scheduled again before calling tasklet_kill().

Unfortunately the updated patch was not released at that time due to
planned rework of Tsi721 mport driver to use threaded interrupts (which
has yet to happen).  Recently the issue was reported again:
https://lkml.org/lkml/2014/2/19/762.

Description from the original Xiaotian's patch:

 "Some drivers use tasklet_disable in device remove/release process,
  tasklet_disable will inc tasklet->count and return.  If the tasklet is
  not handled yet under some softirq pressure, the tasklet will be
  placed on the tasklet_vec, never have a chance to be excuted.  This
  might lead to a heavy loaded ksoftirqd, wakeup with pending_softirq,
  but tasklet is disabled.  tasklet_kill should be used in this case."

This patch is applicable to kernel versions starting from v3.5.

Signed-off-by: Alexandre Bounine <alexandre.bounine at idt.com>
Cc: Matt Porter <mporter at kernel.crashing.org>
Cc: Xiaotian Feng <xtfeng at gmail.com>
Reviewed-by: Thomas Gleixner <tglx at linutronix.de>
Cc: Mike Galbraith <bitbucket at online.de>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/rapidio/devices/tsi721.h     |  1 +
 drivers/rapidio/devices/tsi721_dma.c | 27 ++++++++++++++++++---------
 2 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/drivers/rapidio/devices/tsi721.h b/drivers/rapidio/devices/tsi721.h
index b4b0d83..7061ac0 100644
--- a/drivers/rapidio/devices/tsi721.h
+++ b/drivers/rapidio/devices/tsi721.h
@@ -678,6 +678,7 @@ struct tsi721_bdma_chan {
 	struct list_head	free_list;
 	dma_cookie_t		completed_cookie;
 	struct tasklet_struct	tasklet;
+	bool			active;
 };

 #endif /* CONFIG_RAPIDIO_DMA_ENGINE */
diff --git a/drivers/rapidio/devices/tsi721_dma.c b/drivers/rapidio/devices/tsi721_dma.c
index 502663f..91245f5 100644
--- a/drivers/rapidio/devices/tsi721_dma.c
+++ b/drivers/rapidio/devices/tsi721_dma.c
@@ -206,8 +206,8 @@ void tsi721_bdma_handler(struct tsi721_bdma_chan *bdma_chan)
 {
 	/* Disable BDMA channel interrupts */
 	iowrite32(0, bdma_chan->regs + TSI721_DMAC_INTE);
-
-	tasklet_schedule(&bdma_chan->tasklet);
+	if (bdma_chan->active)
+		tasklet_schedule(&bdma_chan->tasklet);
 }

 #ifdef CONFIG_PCI_MSI
@@ -562,7 +562,7 @@ static int tsi721_alloc_chan_resources(struct dma_chan *dchan)
 	}
 #endif /* CONFIG_PCI_MSI */

-	tasklet_enable(&bdma_chan->tasklet);
+	bdma_chan->active = true;
 	tsi721_bdma_interrupt_enable(bdma_chan, 1);

 	return bdma_chan->bd_num - 1;
@@ -576,9 +576,7 @@ err_out:
 static void tsi721_free_chan_resources(struct dma_chan *dchan)
 {
 	struct tsi721_bdma_chan *bdma_chan = to_tsi721_chan(dchan);
-#ifdef CONFIG_PCI_MSI
 	struct tsi721_device *priv = to_tsi721(dchan->device);
-#endif
 	LIST_HEAD(list);

 	dev_dbg(dchan->device->dev, "%s: Entry\n", __func__);
@@ -589,14 +587,25 @@ static void tsi721_free_chan_resources(struct dma_chan *dchan)
 	BUG_ON(!list_empty(&bdma_chan->active_list));
 	BUG_ON(!list_empty(&bdma_chan->queue));

-	tasklet_disable(&bdma_chan->tasklet);
+	tsi721_bdma_interrupt_enable(bdma_chan, 0);
+	bdma_chan->active = false;
+
+#ifdef CONFIG_PCI_MSI
+	if (priv->flags & TSI721_USING_MSIX) {
+		synchronize_irq(priv->msix[TSI721_VECT_DMA0_DONE +
+					   bdma_chan->id].vector);
+		synchronize_irq(priv->msix[TSI721_VECT_DMA0_INT +
+					   bdma_chan->id].vector);
+	} else
+#endif
+	synchronize_irq(priv->pdev->irq);
+
+	tasklet_kill(&bdma_chan->tasklet);

 	spin_lock_bh(&bdma_chan->lock);
 	list_splice_init(&bdma_chan->free_list, &list);
 	spin_unlock_bh(&bdma_chan->lock);

-	tsi721_bdma_interrupt_enable(bdma_chan, 0);
-
 #ifdef CONFIG_PCI_MSI
 	if (priv->flags & TSI721_USING_MSIX) {
 		free_irq(priv->msix[TSI721_VECT_DMA0_DONE +
@@ -790,6 +799,7 @@ int tsi721_register_dma(struct tsi721_device *priv)
 		bdma_chan->dchan.cookie = 1;
 		bdma_chan->dchan.chan_id = i;
 		bdma_chan->id = i;
+		bdma_chan->active = false;

 		spin_lock_init(&bdma_chan->lock);

@@ -799,7 +809,6 @@ int tsi721_register_dma(struct tsi721_device *priv)

 		tasklet_init(&bdma_chan->tasklet, tsi721_dma_tasklet,
 			     (unsigned long)bdma_chan);
-		tasklet_disable(&bdma_chan->tasklet);
 		list_add_tail(&bdma_chan->dchan.device_node,
 			      &mport->dma.channels);
 	}
--
1.8.3.2