linux-kernel - [PATCH 33/98] drivers/dma/pl330.c: fix locking in pl330_free_chan

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Message-Id: <1373552708-15235-34-git-send-email-luis.henriques@canonical.com>
Date:	Thu, 11 Jul 2013 15:24:03 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
	Kyungmin Park <kyungmin.park@...sung.com>,
	Vinod Koul <vinod.koul@...ux.intel.com>,
	Tomasz Figa <t.figa@...sung.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 33/98] drivers/dma/pl330.c: fix locking in pl330_free_chan_resources()

3.5.7.17 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>

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@...sung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@...sung.com>
Acked-by: Jassi Brar <jassisinghbrar@...il.com>
Cc: Vinod Koul <vinod.koul@...ux.intel.com>
Cc: Tomasz Figa <t.figa@...sung.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques@...onical.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 f5843bc..de4ec1a 100644
--- a/drivers/dma/pl330.c
+++ b/drivers/dma/pl330.c
@@ -2462,10 +2462,10 @@ 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

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