[CFT 01/11] dmaengine: add OMAP DMA engine driver

On Fri, Jun 08, 2012 at 03:30:23PM +0530, Shilimkar, Santosh wrote:

On Fri, Jun 8, 2012 at 2:32 PM, Russell King - ARM Linux
[off-list ref] wrote:

quoted

On Thu, Jun 07, 2012 at 12:06:32PM +0100, Russell King wrote:

quoted

Tested-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Russell King <redacted>
---
?drivers/dma/Kconfig ? ? ?| ? ?6 +
?drivers/dma/Makefile ? ? | ? ?1 +
?drivers/dma/omap-dma.c ? | ?522 ++++++++++++++++++++++++++++++++++++++++++++++
?include/linux/omap-dma.h | ? 24 ++
?4 files changed, 553 insertions(+), 0 deletions(-)
?create mode 100644 drivers/dma/omap-dma.c
?create mode 100644 include/linux/omap-dma.h

There is a bug in here which no one has spotted... I just noticed it.

diff --git a/drivers/dma/omap-dma.c b/drivers/dma/omap-dma.c
index 500bc71..02eb2fd 100644
--- a/drivers/dma/omap-dma.c
+++ b/drivers/dma/omap-dma.c

@@ -130,14 +130,13 @@ static void omap_dma_callback(int ch, u16 status, void *data)

? ? ? ?spin_lock_irqsave(&c->vc.lock, flags);
? ? ? ?d = c->desc;
- ? ? ? if (!d)
- ? ? ? ? ? ? ? return;
-
- ? ? ? if (++c->sgidx < d->sglen) {
- ? ? ? ? ? ? ? omap_dma_start_sg(c, d, c->sgidx);
- ? ? ? } else {
- ? ? ? ? ? ? ? omap_dma_start_desc(c);
- ? ? ? ? ? ? ? vchan_cookie_complete(&d->vd);
+ ? ? ? if (d) {
+ ? ? ? ? ? ? ? if (++c->sgidx < d->sglen) {
+ ? ? ? ? ? ? ? ? ? ? ? omap_dma_start_sg(c, d, c->sgidx);
+ ? ? ? ? ? ? ? } else {
+ ? ? ? ? ? ? ? ? ? ? ? omap_dma_start_desc(c);
+ ? ? ? ? ? ? ? ? ? ? ? vchan_cookie_complete(&d->vd);
+ ? ? ? ? ? ? ? }
? ? ? ?}
? ? ? ?spin_unlock_irqrestore(&c->vc.lock, flags);
?}

You mean the lock release, right ?

Yes, if c->desc is NULL, we exit this function with the lock held,
which will lead to a lockup.