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Date: Sat, 26 Nov 2011 12:54:08 +0200
From: Mika Westerberg <mika.westerberg@....fi>
To: linux-kernel@...r.kernel.org
Cc: vinod.koul@...el.com, dan.j.williams@...el.com,
hsweeten@...ionengravers.com, rmallon@...il.com,
Rafal Prylowski <prylowski@...asoft.pl>,
Mika Westerberg <mika.westerberg@....fi>
Subject: [PATCH v2 2/2] dma/ep93xx_dma: prevent ep93xx_dma_tasklet() to reference an empty list
If dma_terminate_all() is called before the ep93xx_dma_tasklet() gets to run,
it tries to access an empty ->active list which results 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)
To make the code a bit more robust against things like these, we modify
ep93xx_dma_get_active() to return NULL in case of empty ->active list and make
sure that callers handle this correctly.
Reported-by: Rafal Prylowski <prylowski@...asoft.pl>
Signed-off-by: Mika Westerberg <mika.westerberg@....fi>
---
drivers/dma/ep93xx_dma.c | 60 ++++++++++++++++++++++++++++++++++++---------
1 files changed, 48 insertions(+), 12 deletions(-)
diff --git a/drivers/dma/ep93xx_dma.c b/drivers/dma/ep93xx_dma.c
index 6181811..745fa8b 100644
--- a/drivers/dma/ep93xx_dma.c
+++ b/drivers/dma/ep93xx_dma.c
@@ -246,6 +246,9 @@ 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)
{
+ if (list_empty(&edmac->active))
+ return NULL;
+
return list_first_entry(&edmac->active, struct ep93xx_dma_desc, node);
}
@@ -263,16 +266,22 @@ ep93xx_dma_get_active(struct ep93xx_dma_chan *edmac)
*/
static bool ep93xx_dma_advance_active(struct ep93xx_dma_chan *edmac)
{
+ struct ep93xx_dma_desc *desc;
+
list_rotate_left(&edmac->active);
if (test_bit(EP93XX_DMA_IS_CYCLIC, &edmac->flags))
return true;
+ desc = ep93xx_dma_get_active(edmac);
+ if (!desc)
+ return false;
+
/*
* If txd.cookie is set it means that we are back in the first
* descriptor in the chain and hence done with it.
*/
- return !ep93xx_dma_get_active(edmac)->txd.cookie;
+ return !desc->txd.cookie;
}
/*
@@ -327,9 +336,15 @@ static void m2p_hw_shutdown(struct ep93xx_dma_chan *edmac)
static void m2p_fill_desc(struct ep93xx_dma_chan *edmac)
{
- struct ep93xx_dma_desc *desc = ep93xx_dma_get_active(edmac);
+ struct ep93xx_dma_desc *desc;
u32 bus_addr;
+ desc = ep93xx_dma_get_active(edmac);
+ if (!desc) {
+ dev_warn(chan2dev(edmac), "M2P: empty descriptor list\n");
+ return;
+ }
+
if (ep93xx_dma_chan_direction(&edmac->chan) == DMA_TO_DEVICE)
bus_addr = desc->src_addr;
else
@@ -491,7 +506,13 @@ static void m2m_hw_shutdown(struct ep93xx_dma_chan *edmac)
static void m2m_fill_desc(struct ep93xx_dma_chan *edmac)
{
- struct ep93xx_dma_desc *desc = ep93xx_dma_get_active(edmac);
+ struct ep93xx_dma_desc *desc;
+
+ desc = ep93xx_dma_get_active(edmac);
+ if (!desc) {
+ dev_warn(chan2dev(edmac), "M2M: empty descriptor list\n");
+ return;
+ }
if (edmac->buffer == 0) {
writel(desc->src_addr, edmac->regs + M2M_SAR_BASE0);
@@ -669,24 +690,30 @@ 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);
+ /*
+ * If dma_terminate_all() was called before we get to run, the active
+ * list has become empty. If that happens we aren't supposed to do
+ * anything more than call ep93xx_dma_advance_work().
+ */
desc = ep93xx_dma_get_active(edmac);
- if (desc->complete) {
- edmac->last_completed = desc->txd.cookie;
- list_splice_init(&edmac->active, &list);
+ if (desc) {
+ 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) {
/*
@@ -706,13 +733,22 @@ static void ep93xx_dma_tasklet(unsigned long data)
static irqreturn_t ep93xx_dma_interrupt(int irq, void *dev_id)
{
struct ep93xx_dma_chan *edmac = dev_id;
+ struct ep93xx_dma_desc *desc;
irqreturn_t ret = IRQ_HANDLED;
spin_lock(&edmac->lock);
+ desc = ep93xx_dma_get_active(edmac);
+ if (!desc) {
+ dev_warn(chan2dev(edmac),
+ "got interrupt while active list is empty\n");
+ spin_unlock(&edmac->lock);
+ return IRQ_NONE;
+ }
+
switch (edmac->edma->hw_interrupt(edmac)) {
case INTERRUPT_DONE:
- ep93xx_dma_get_active(edmac)->complete = true;
+ desc->complete = true;
tasklet_schedule(&edmac->tasklet);
break;
--
1.7.7
--
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