[ 3.8.y.z extended stable ] Patch "drivers/dma/pl330.c: fix locking in" has been added to staging queue

[Luis Henriques]

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

    drivers/dma/pl330.c: fix locking in

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

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.
-Luis

------

>From 407a902cf45efc564b4e39ccd06f2029e534eef3 Mon Sep 17 00:00:00 2001
From: Bartlomiej Zolnierkiewicz <b.zolnierkie at samsung.com>
Date: Wed, 3 Jul 2013 15:00:43 -0700
Subject: [PATCH] drivers/dma/pl330.c: fix locking in
 pl330_free_chan_resources()

commit da331ba8e9c5de72a27e50f71105395bba6eebe0 upstream.

tasklet_kill() may sleep so call it before taking pch->lock.

Fixes following lockup:

  BUG: scheduling while atomic: cat/2383/0x00000002
  Modules linked in:
    unwind_backtrace+0x0/0xfc
    __schedule_bug+0x4c/0x58
    __schedule+0x690/0x6e0
    sys_sched_yield+0x70/0x78
    tasklet_kill+0x34/0x8c
    pl330_free_chan_resources+0x24/0x88
    dma_chan_put+0x4c/0x50
  [...]
  BUG: spinlock lockup suspected on CPU#0, swapper/0/0
   lock: 0xe52aa04c, .magic: dead4ead, .owner: cat/2383, .owner_cpu: 1
    unwind_backtrace+0x0/0xfc
    do_raw_spin_lock+0x194/0x204
    _raw_spin_lock_irqsave+0x20/0x28
    pl330_tasklet+0x2c/0x5a8
    tasklet_action+0xfc/0x114
    __do_softirq+0xe4/0x19c
    irq_exit+0x98/0x9c
    handle_IPI+0x124/0x16c
    gic_handle_irq+0x64/0x68
    __irq_svc+0x40/0x70
    cpuidle_wrap_enter+0x4c/0xa0
    cpuidle_enter_state+0x18/0x68
    cpuidle_idle_call+0xac/0xe0
    cpu_idle+0xac/0xf0

Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie at samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park at samsung.com>
Acked-by: Jassi Brar <jassisinghbrar at gmail.com>
Cc: Vinod Koul <vinod.koul at linux.intel.com>
Cc: Tomasz Figa <t.figa at samsung.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/dma/pl330.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
index 80680ee..4bed3f1 100644
--- a/drivers/dma/pl330.c
+++ b/drivers/dma/pl330.c
@@ -2459,10 +2459,10 @@ static void pl330_free_chan_resources(struct dma_chan *chan)
 	struct dma_pl330_chan *pch = to_pchan(chan);
 	unsigned long flags;

-	spin_lock_irqsave(&pch->lock, flags);
-
 	tasklet_kill(&pch->task);

+	spin_lock_irqsave(&pch->lock, flags);
+
 	pl330_release_channel(pch->pl330_chid);
 	pch->pl330_chid = NULL;

--
1.8.1.2