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authorRussell King - ARM Linux2011-01-03 22:41:34 +0000
committerDan Williams2011-01-04 19:16:13 -0800
commit858c21c0f380fb9c78f47f3e372f9baadc54dffe (patch)
tree236ca2bf8b319a38ad7d0988491a64add47d5b55 /drivers/dma
parent30749cb4a40f02a199640011e5ab5c5f60b8482e (diff)
ARM: PL08x: move callback outside spinlock'd region
Calling the callback handler with spinlocks in the tasklet held leads to deadlock when dmaengine functions are called: BUG: spinlock lockup on CPU#0, sh/417, c1870a08 Backtrace: ... [<c017b408>] (do_raw_spin_lock+0x0/0x154) from [<c02c4b98>] (_raw_spin_lock_irqsave+0x54/0x60) [<c02c4b44>] (_raw_spin_lock_irqsave+0x0/0x60) from [<c01f5828>] (pl08x_prep_channel_resources+0x718/0x8b4) [<c01f5110>] (pl08x_prep_channel_resources+0x0/0x8b4) from [<c01f5bb4>] (pl08x_prep_slave_sg+0x120/0x19c) [<c01f5a94>] (pl08x_prep_slave_sg+0x0/0x19c) from [<c01be7a0>] (pl011_dma_tx_refill+0x164/0x224) [<c01be63c>] (pl011_dma_tx_refill+0x0/0x224) from [<c01bf1c8>] (pl011_dma_tx_callback+0x7c/0xc4) [<c01bf14c>] (pl011_dma_tx_callback+0x0/0xc4) from [<c01f4d34>] (pl08x_tasklet+0x60/0x368) [<c01f4cd4>] (pl08x_tasklet+0x0/0x368) from [<c004d978>] (tasklet_action+0xa0/0x100) Dan quoted the documentation: > 2/ Completion callback routines cannot submit new operations.  This >    results in recursion in the synchronous case and spin_locks being >    acquired twice in the asynchronous case. but then followed up to say: > I should clarify, this is the async_memcpy() api requirement which is > not used outside of md/raid5. DMA drivers can and do allow new > submissions from callbacks, and the ones that do so properly move the > callback outside of the driver lock. So let's fix it by moving the callback out of the spinlocked region. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk> Acked-by: Linus Walleij <linus.walleij@stericsson.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'drivers/dma')
-rw-r--r--drivers/dma/amba-pl08x.c29
1 files changed, 15 insertions, 14 deletions
diff --git a/drivers/dma/amba-pl08x.c b/drivers/dma/amba-pl08x.c
index 986c12775b0b..660165dd945a 100644
--- a/drivers/dma/amba-pl08x.c
+++ b/drivers/dma/amba-pl08x.c
@@ -1540,32 +1540,29 @@ static void pl08x_tasklet(unsigned long data)
{
struct pl08x_dma_chan *plchan = (struct pl08x_dma_chan *) data;
struct pl08x_driver_data *pl08x = plchan->host;
+ struct pl08x_txd *txd;
+ dma_async_tx_callback callback = NULL;
+ void *callback_param = NULL;
unsigned long flags;
spin_lock_irqsave(&plchan->lock, flags);
- if (plchan->at) {
- dma_async_tx_callback callback =
- plchan->at->tx.callback;
- void *callback_param =
- plchan->at->tx.callback_param;
+ txd = plchan->at;
+ plchan->at = NULL;
- /*
- * Update last completed
- */
- plchan->lc = plchan->at->tx.cookie;
+ if (txd) {
+ callback = txd->tx.callback;
+ callback_param = txd->tx.callback_param;
/*
- * Callback to signal completion
+ * Update last completed
*/
- if (callback)
- callback(callback_param);
+ plchan->lc = txd->tx.cookie;
/*
* Free the descriptor
*/
- pl08x_free_txd(pl08x, plchan->at);
- plchan->at = NULL;
+ pl08x_free_txd(pl08x, txd);
}
/*
* If a new descriptor is queued, set it up
@@ -1616,6 +1613,10 @@ static void pl08x_tasklet(unsigned long data)
}
spin_unlock_irqrestore(&plchan->lock, flags);
+
+ /* Callback to signal completion */
+ if (callback)
+ callback(callback_param);
}
static irqreturn_t pl08x_irq(int irq, void *dev)