[PATCH 2/2] dma/ep93xx_dma: prevent ep93xx_dma_tasklet() to access empty list
From: Mika Westerberg
Date: Tue Nov 22 2011 - 14:46:03 EST
From: Rafal Prylowski <prylowski@xxxxxxxxxxx>
If dma_terminate_all() is called before the ep93xx_dma_tasklet() gets to run,
it tries to access an empty ->active list causing following OOPS:
Internal error: Oops - undefined instruction: 0 [#1]
CPU: 0 Not tainted (3.2.0-rc1EP-1+ #1008)
PC is at 0xc184c868
LR is at ep93xx_dma_tasklet+0xec/0x164
pc : [<c184c868>] lr : [<c012b528>] psr: 00000013
sp : c02b7e70 ip : ffffffff fp : c02b7ea4
r10: 00000100 r9 : 80000013 r8 : c02b7e50
r7 : c02b7e70 r6 : c02b7ea4 r5 : 000000a4 r4 : c02b7e70
r3 : c02b751d r2 : 8ae34598 r1 : c184c6e0 r0 : c02b7ea4
Flags: nzcv IRQs on FIQs on Mode SVC_32 ISA ARM Segment kernel
Control: c000717f Table: c0004000 DAC: 00000017
Process swapper (pid: 0, stack limit = 0xc02b6270)
Stack: (0xc02b7e70 to 0xc02b8000)
7e60: c02b7ea4 c02b7e70 c0008b64 c02bd5c4
7e80: c02d60e0 00000000 00000000 c02bd44c c02d60e0 00000100 c02b7ec4 c02b7ea8
7ea0: c001c49c c012b44c 00000018 00000001 c02d60e0 c02b6000 c02b7f04 c02b7ec8
7ec0: c001cbc0 c001c3e4 c02b7eec c02b7ed8 00000006 0000000a c02bf674 c02c458c
7ee0: 00000011 00000000 c02b7f7c c0004000 41129200 c02b0c80 c02b7f14 c02b7f08
7f00: c001cdd0 c001cb38 c02b7f34 c02b7f18 c000983c c001cd98 c0009a60 60000013
7f20: fefb0001 c02b7f7c c02b7f44 c02b7f38 c0008190 c0009810 c02b7f9c c02b7f48
7f40: c0008b64 c0008190 c02c2bf8 00000002 c02b7f90 60000013 c02b6000 c02d1504
7f60: c02baa88 c02baa80 c0004000 41129200 c02b0c80 c02b7f9c c02b7fa0 c02b7f90
7f80: c0009a54 c0009a60 60000013 ffffffff c02b7fbc c02b7fa0 c000a03c c0009a40
7fa0: c02b80b0 c02b19dc c02b19d8 c02baa80 c02b7fcc c02b7fc0 c02384e4 c0009fd4
7fc0: c02b7ff4 c02b7fd0 c029d924 c0238494 c029d49c 00000000 00000000 c02b19dc
7fe0: c0007175 c02b803c 00000000 c02b7ff8 c000803c c029d700 00000000 00000000
Backtrace:
[<c012b43c>] (ep93xx_dma_tasklet+0x0/0x164) from [<c001c49c>] (tasklet_action+0xc8/0xdc)
[<c001c3d4>] (tasklet_action+0x0/0xdc) from [<c001cbc0>] (__do_softirq+0x98/0x154)
r7:c02b6000 r6:c02d60e0 r5:00000001 r4:00000018
[<c001cb28>] (__do_softirq+0x0/0x154) from [<c001cdd0>] (irq_exit+0x48/0x50)
[<c001cd88>] (irq_exit+0x0/0x50) from [<c000983c>] (handle_IRQ+0x3c/0x8c)
[<c0009800>] (handle_IRQ+0x0/0x8c) from [<c0008190>] (asm_do_IRQ+0x10/0x14)
r7:c02b7f7c r6:fefb0001 r5:60000013 r4:c0009a60
[<c0008180>] (asm_do_IRQ+0x0/0x14) from [<c0008b64>] (__irq_svc+0x24/0xc0)
Exception stack(0xc02b7f48 to 0xc02b7f90)
7f40: c02c2bf8 00000002 c02b7f90 60000013 c02b6000 c02d1504
7f60: c02baa88 c02baa80 c0004000 41129200 c02b0c80 c02b7f9c c02b7fa0 c02b7f90
7f80: c0009a54 c0009a60 60000013 ffffffff
[<c0009a30>] (default_idle+0x0/0x34) from [<c000a03c>] (cpu_idle+0x78/0xb0)
[<c0009fc4>] (cpu_idle+0x0/0xb0) from [<c02384e4>] (rest_init+0x60/0x78)
r7:c02baa80 r6:c02b19d8 r5:c02b19dc r4:c02b80b0
[<c0238484>] (rest_init+0x0/0x78) from [<c029d924>] (start_kernel+0x234/0x278)
[<c029d6f0>] (start_kernel+0x0/0x278) from [<c000803c>] (0xc000803c)
r5:c02b803c r4:c0007175
Code: 42555300 54535953 643d4d45 65766972 (53007372)
As we expect that the ->active list is never empty when the ep93xx_dma_tasklet()
is called, we fix this by adding a new flag per channel EP93XX_DMA_IS_RUNNING
which determines whether the channel is running or not.
We also add BUG_ON() to ep93xx_dma_get_active() to make sure that similar
problems will be caught early.
Signed-off-by: Rafal Prylowski <prylowski@xxxxxxxxxxx>
[added a flag instead of just checking for empty list]
Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxx>
---
drivers/dma/ep93xx_dma.c | 25 ++++++++++++++++---------
1 files changed, 16 insertions(+), 9 deletions(-)
diff --git a/drivers/dma/ep93xx_dma.c b/drivers/dma/ep93xx_dma.c
index 6181811..cc3a302 100644
--- a/drivers/dma/ep93xx_dma.c
+++ b/drivers/dma/ep93xx_dma.c
@@ -155,6 +155,8 @@ struct ep93xx_dma_chan {
unsigned long flags;
/* Channel is configured for cyclic transfers */
#define EP93XX_DMA_IS_CYCLIC 0
+/* Channel is enabled */
+#define EP93XX_DMA_IS_RUNNING 1
int buffer;
dma_cookie_t last_completed;
@@ -246,6 +248,7 @@ static void ep93xx_dma_set_active(struct ep93xx_dma_chan *edmac,
static struct ep93xx_dma_desc *
ep93xx_dma_get_active(struct ep93xx_dma_chan *edmac)
{
+ BUG_ON(list_empty(&edmac->active));
return list_first_entry(&edmac->active, struct ep93xx_dma_desc, node);
}
@@ -669,24 +672,25 @@ static void ep93xx_dma_tasklet(unsigned long data)
{
struct ep93xx_dma_chan *edmac = (struct ep93xx_dma_chan *)data;
struct ep93xx_dma_desc *desc, *d;
- dma_async_tx_callback callback;
- void *callback_param;
+ dma_async_tx_callback callback = NULL;
+ void *callback_param = NULL;
LIST_HEAD(list);
spin_lock_irq(&edmac->lock);
- desc = ep93xx_dma_get_active(edmac);
- if (desc->complete) {
- edmac->last_completed = desc->txd.cookie;
- list_splice_init(&edmac->active, &list);
+ if (test_bit(EP93XX_DMA_IS_RUNNING, &edmac->flags)) {
+ desc = ep93xx_dma_get_active(edmac);
+ if (desc->complete) {
+ edmac->last_completed = desc->txd.cookie;
+ list_splice_init(&edmac->active, &list);
+ }
+ callback = desc->txd.callback;
+ callback_param = desc->txd.callback_param;
}
spin_unlock_irq(&edmac->lock);
/* Pick up the next descriptor from the queue */
ep93xx_dma_advance_work(edmac);
- callback = desc->txd.callback;
- callback_param = desc->txd.callback_param;
-
/* Now we can release all the chained descriptors */
list_for_each_entry_safe(desc, d, &list, node) {
/*
@@ -758,6 +762,8 @@ static dma_cookie_t ep93xx_dma_tx_submit(struct dma_async_tx_descriptor *tx)
edmac->chan.cookie = cookie;
desc->txd.cookie = cookie;
+ set_bit(EP93XX_DMA_IS_RUNNING, &edmac->flags);
+
/*
* If nothing is currently prosessed, we push this descriptor
* directly to the hardware. Otherwise we put the descriptor
@@ -1106,6 +1112,7 @@ static int ep93xx_dma_terminate_all(struct ep93xx_dma_chan *edmac)
spin_lock_irqsave(&edmac->lock, flags);
/* First we disable and flush the DMA channel */
edmac->edma->hw_shutdown(edmac);
+ clear_bit(EP93XX_DMA_IS_RUNNING, &edmac->flags);
clear_bit(EP93XX_DMA_IS_CYCLIC, &edmac->flags);
list_splice_init(&edmac->active, &list);
list_splice_init(&edmac->queue, &list);
--
1.7.7
--
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