* [PATCH] [FIX] dmaengine: virt-dma: Free descriptor after callback
@ 2014-04-18 0:56 ` Joel Fernandes
0 siblings, 0 replies; 7+ messages in thread
From: Joel Fernandes @ 2014-04-18 0:56 UTC (permalink / raw)
To: dmaengine, linux-kernel, linux-omap, davinci-linux-open-source
Cc: Joel Fernandes, Vinod Koul, Dan Williams, Russell King
Free the vd (virt descriptor) after the callback is called. In EDMA driver
atleast which uses virt-dma, we make use of the desc during the callback and if
its dangerously freed before the callback is called. I also noticed this in
omap-dma dmaengine driver.
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Joel Fernandes <joelf@ti.com>
---
drivers/dma/virt-dma.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/dma/virt-dma.c b/drivers/dma/virt-dma.c
index 6f80432..98aeb7f 100644
--- a/drivers/dma/virt-dma.c
+++ b/drivers/dma/virt-dma.c
@@ -84,10 +84,10 @@ static void vchan_complete(unsigned long arg)
list_del(&vd->node);
- vc->desc_free(vd);
-
if (cb)
cb(cb_data);
+
+ vc->desc_free(vd);
}
}
--
1.7.9.5
^ permalink raw reply related [flat|nested] 7+ messages in thread
* [PATCH] [FIX] dmaengine: virt-dma: Free descriptor after callback
@ 2014-04-18 0:56 ` Joel Fernandes
0 siblings, 0 replies; 7+ messages in thread
From: Joel Fernandes @ 2014-04-18 0:56 UTC (permalink / raw)
To: dmaengine, linux-kernel, linux-omap, davinci-linux-open-source
Cc: Joel Fernandes, Vinod Koul, Dan Williams, Russell King
Free the vd (virt descriptor) after the callback is called. In EDMA driver
atleast which uses virt-dma, we make use of the desc during the callback and if
its dangerously freed before the callback is called. I also noticed this in
omap-dma dmaengine driver.
Cc: Vinod Koul <vinod.koul@intel.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Joel Fernandes <joelf@ti.com>
---
drivers/dma/virt-dma.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/dma/virt-dma.c b/drivers/dma/virt-dma.c
index 6f80432..98aeb7f 100644
--- a/drivers/dma/virt-dma.c
+++ b/drivers/dma/virt-dma.c
@@ -84,10 +84,10 @@ static void vchan_complete(unsigned long arg)
list_del(&vd->node);
- vc->desc_free(vd);
-
if (cb)
cb(cb_data);
+
+ vc->desc_free(vd);
}
}
--
1.7.9.5
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] [FIX] dmaengine: virt-dma: Free descriptor after callback
@ 2014-04-18 8:50 ` Russell King - ARM Linux
0 siblings, 0 replies; 7+ messages in thread
From: Russell King - ARM Linux @ 2014-04-18 8:50 UTC (permalink / raw)
To: Joel Fernandes
Cc: dmaengine, linux-kernel, linux-omap, davinci-linux-open-source,
Vinod Koul, Dan Williams
On Thu, Apr 17, 2014 at 07:56:50PM -0500, Joel Fernandes wrote:
> Free the vd (virt descriptor) after the callback is called. In EDMA driver
> atleast which uses virt-dma, we make use of the desc during the callback and if
> its dangerously freed before the callback is called. I also noticed this in
> omap-dma dmaengine driver.
You've missed the vital bit of information: why do you make use of the
descriptor afterwards? You shouldn't. omap-dma doesn't either.
Once clients submit their request to DMA engine, they must not hold any
kind of reference to the descriptor other than the cookie.
--
FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly
improving, and getting towards what was expected from it.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] [FIX] dmaengine: virt-dma: Free descriptor after callback
@ 2014-04-18 8:50 ` Russell King - ARM Linux
0 siblings, 0 replies; 7+ messages in thread
From: Russell King - ARM Linux @ 2014-04-18 8:50 UTC (permalink / raw)
To: Joel Fernandes
Cc: davinci-linux-open-source-VycZQUHpC/PFrsHnngEfi1aTQe2KTcn/,
Vinod Koul, linux-kernel-u79uwXL29TY76Z2rM5mHXA,
dmaengine-u79uwXL29TY76Z2rM5mHXA, Dan Williams,
linux-omap-u79uwXL29TY76Z2rM5mHXA
On Thu, Apr 17, 2014 at 07:56:50PM -0500, Joel Fernandes wrote:
> Free the vd (virt descriptor) after the callback is called. In EDMA driver
> atleast which uses virt-dma, we make use of the desc during the callback and if
> its dangerously freed before the callback is called. I also noticed this in
> omap-dma dmaengine driver.
You've missed the vital bit of information: why do you make use of the
descriptor afterwards? You shouldn't. omap-dma doesn't either.
Once clients submit their request to DMA engine, they must not hold any
kind of reference to the descriptor other than the cookie.
--
FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly
improving, and getting towards what was expected from it.
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] [FIX] dmaengine: virt-dma: Free descriptor after callback
2014-04-18 8:50 ` Russell King - ARM Linux
@ 2014-04-18 16:34 ` Joel Fernandes
-1 siblings, 0 replies; 7+ messages in thread
From: Joel Fernandes @ 2014-04-18 16:34 UTC (permalink / raw)
To: Russell King - ARM Linux
Cc: dmaengine, linux-kernel, linux-omap, davinci-linux-open-source,
Vinod Koul, Dan Williams
On 04/18/2014 03:50 AM, Russell King - ARM Linux wrote:
> On Thu, Apr 17, 2014 at 07:56:50PM -0500, Joel Fernandes wrote:
>> Free the vd (virt descriptor) after the callback is called. In EDMA driver
>> atleast which uses virt-dma, we make use of the desc during the callback and if
>> its dangerously freed before the callback is called. I also noticed this in
>> omap-dma dmaengine driver.
>
> You've missed the vital bit of information: why do you make use of the
> descriptor afterwards? You shouldn't. omap-dma doesn't either.
>
> Once clients submit their request to DMA engine, they must not hold any
> kind of reference to the descriptor other than the cookie.
>
Sorry, I confused edma/omap-dma callbacks for virt dma callbacks.
Anyway, I think there is still a chance in edma that we refer to the
echan->edesc pointer later on after virt-dma calls the free (in
edma_execute), so I'll just NULL that out to be safe and submit a patch.
Thanks.
regards,
-Joel
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] [FIX] dmaengine: virt-dma: Free descriptor after callback
@ 2014-04-18 16:34 ` Joel Fernandes
0 siblings, 0 replies; 7+ messages in thread
From: Joel Fernandes @ 2014-04-18 16:34 UTC (permalink / raw)
To: Russell King - ARM Linux
Cc: dmaengine, linux-kernel, linux-omap, davinci-linux-open-source,
Vinod Koul, Dan Williams
On 04/18/2014 03:50 AM, Russell King - ARM Linux wrote:
> On Thu, Apr 17, 2014 at 07:56:50PM -0500, Joel Fernandes wrote:
>> Free the vd (virt descriptor) after the callback is called. In EDMA driver
>> atleast which uses virt-dma, we make use of the desc during the callback and if
>> its dangerously freed before the callback is called. I also noticed this in
>> omap-dma dmaengine driver.
>
> You've missed the vital bit of information: why do you make use of the
> descriptor afterwards? You shouldn't. omap-dma doesn't either.
>
> Once clients submit their request to DMA engine, they must not hold any
> kind of reference to the descriptor other than the cookie.
>
Sorry, I confused edma/omap-dma callbacks for virt dma callbacks.
Anyway, I think there is still a chance in edma that we refer to the
echan->edesc pointer later on after virt-dma calls the free (in
edma_execute), so I'll just NULL that out to be safe and submit a patch.
Thanks.
regards,
-Joel
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] [FIX] dmaengine: virt-dma: Free descriptor after callback
2014-04-18 16:34 ` Joel Fernandes
(?)
@ 2014-04-22 16:14 ` Vinod Koul
-1 siblings, 0 replies; 7+ messages in thread
From: Vinod Koul @ 2014-04-22 16:14 UTC (permalink / raw)
To: Joel Fernandes
Cc: Russell King - ARM Linux, dmaengine, linux-kernel, linux-omap,
davinci-linux-open-source, Dan Williams
On Fri, Apr 18, 2014 at 11:34:50AM -0500, Joel Fernandes wrote:
> On 04/18/2014 03:50 AM, Russell King - ARM Linux wrote:
> > On Thu, Apr 17, 2014 at 07:56:50PM -0500, Joel Fernandes wrote:
> >> Free the vd (virt descriptor) after the callback is called. In EDMA driver
> >> atleast which uses virt-dma, we make use of the desc during the callback and if
> >> its dangerously freed before the callback is called. I also noticed this in
> >> omap-dma dmaengine driver.
> >
> > You've missed the vital bit of information: why do you make use of the
> > descriptor afterwards? You shouldn't. omap-dma doesn't either.
> >
> > Once clients submit their request to DMA engine, they must not hold any
> > kind of reference to the descriptor other than the cookie.
> >
>
> Sorry, I confused edma/omap-dma callbacks for virt dma callbacks.
>
> Anyway, I think there is still a chance in edma that we refer to the
> echan->edesc pointer later on after virt-dma calls the free (in
> edma_execute), so I'll just NULL that out to be safe and submit a patch.
Yes, that would be the right way :)
While looking at this, I see it is not called out specfically in documentation, will update
that as well
--
~Vinod
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2014-04-22 16:26 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2014-04-18 0:56 [PATCH] [FIX] dmaengine: virt-dma: Free descriptor after callback Joel Fernandes
2014-04-18 0:56 ` Joel Fernandes
2014-04-18 8:50 ` Russell King - ARM Linux
2014-04-18 8:50 ` Russell King - ARM Linux
2014-04-18 16:34 ` Joel Fernandes
2014-04-18 16:34 ` Joel Fernandes
2014-04-22 16:14 ` Vinod Koul
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