During DMA client(UART) stress testing, observed below crash:
[ 167.041591] Unable to handle kernel paging request at virtual address 00100108
[ 167.048818] pgd = ffffffc0de7ee000
[ 167.052222] [00100108] *pgd=0000000000000000
[ 167.056513] Internal error: Oops: 96000045 [#1] PREEMPT SMP
[ 167.084048] Modules linked in:
[ 167.087126] CPU: 0 PID: 1786 Comm: uarttest Tainted: G W 3.10.33-gb76f6f9 #5
[ 167.095040] task: ffffffc0a5ba6ac0 ti: ffffffc094380000 task.ti: ffffffc094380000
[ 167.102529] PC is at tegra_dma_tasklet+0x50/0xf4
[ 167.107148] LR is at tegra_dma_tasklet+0xc0/0xf4
[ 167.111767] pc : [<ffffffc00044acc8>] lr : [<ffffffc00044ad38>] pstate: 800001c5
[ 167.119155] sp : ffffffc094383a60
[ 167.122469] x29: ffffffc094383a60 x28: 0000000000000000
Issue: UART RX channel DMA completion EOC(End of completion) interrupt
occurs and dma driver schedules tasklet() to execute callback function
and empty the cb_desc (callback descriptor). Before dma driver tasklet
runs, UART RX EORD (end of receive data) interrupt occurs. Here UART RX
ISR handler calls tegra_dma_terminate_all() and re-configures the DMA
for RX. While re-configuring, the cb_node data is re-initialized but the
cb_desc list is not emptied. Now when dma driver tasklet callback function
tries to check cb_desc and delete the cb_node (re-initialized node) kernel
crashes.
Fix: Empty the cb_desc data structure during tegra_dma_terminate_all()
routine if there are no pending transfers.
Signed-off-by: Shardar Shariff Md <smohammed@xxxxxxxxxx>
---
drivers/dma/tegra20-apb-dma.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/drivers/dma/tegra20-apb-dma.c b/drivers/dma/tegra20-apb-dma.c
index 3871f29..34bb4cd 100644
--- a/drivers/dma/tegra20-apb-dma.c
+++ b/drivers/dma/tegra20-apb-dma.c
@@ -751,10 +751,8 @@ static int tegra_dma_terminate_all(struct dma_chan *dc)
bool was_busy;
spin_lock_irqsave(&tdc->lock, flags);
- if (list_empty(&tdc->pending_sg_req)) {
- spin_unlock_irqrestore(&tdc->lock, flags);
- return 0;
- }
+ if (list_empty(&tdc->pending_sg_req))
+ goto empty_cblist;
if (!tdc->busy)
goto skip_dma_stop;
@@ -787,6 +785,7 @@ static int tegra_dma_terminate_all(struct dma_chan *dc)
skip_dma_stop:
tegra_dma_abort_all(tdc);
+empty_cblist:
while (!list_empty(&tdc->cb_desc)) {
dma_desc = list_first_entry(&tdc->cb_desc,
typeof(*dma_desc), cb_node);
--
1.8.1.5
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