On 10/27/07, Dan Williams <[EMAIL PROTECTED]> wrote: > On Sat, 2007-10-27 at 06:49 -0700, Haavard Skinnemoen wrote: > > On Fri, 26 Oct 2007 09:36:17 -0700 > > Dan Williams <[EMAIL PROTECTED]> wrote: > > > > > @@ -221,7 +220,6 @@ void dma_chan_cleanup(struct kref *kref) > > > { > > > struct dma_chan *chan = container_of(kref, struct dma_chan, > > > refcount); > > > chan->device->device_free_chan_resources(chan); > > > - kref_put(&chan->device->refcount, dma_async_device_cleanup); > > > } > > > EXPORT_SYMBOL(dma_chan_cleanup); > > > > While I can't see any problems with the rest of the patch, I think this > > part is wrong for the same reasons removing the kref_put() from the > > class device cleanup function is. I don't see any constraint that > > guarantees that dma_chan_cleanup() will always be called before > > dma_dev_release(), which means that "chan" may have been freed before > > this function gets a chance to run. Please correct me if I'm wrong. > > Absolutely right, the driver, not dmaengine, frees the memory so there > must be a per channel reference on the device to hold off the driver's > remove routine. > > > > HÃ¥vard > > So how about this... > > ---snip--- > dmaengine: Fix broken device refcounting > > From: Haavard Skinnemoen <[EMAIL PROTECTED]> > > When a DMA device is unregistered, its reference count is decremented > twice for each channel: Once dma_class_dev_release() and once in > dma_chan_cleanup(). This may result in the DMA device driver's > remove() function completing before all channels have been cleaned > up, causing lots of use-after-free fun. > > Fix it by incrementing the device's reference count twice for each > channel during registration. > > Signed-off-by: Haavard Skinnemoen <[EMAIL PROTECTED]> > [EMAIL PROTECTED]: kill unnecessary client refcounting] > Signed-off-by: Dan Williams <[EMAIL PROTECTED]> > --- > > drivers/dma/dmaengine.c | 17 ++++++----------- > 1 files changed, 6 insertions(+), 11 deletions(-) > > diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c > index 84257f7..ec7e871 100644 > --- a/drivers/dma/dmaengine.c > +++ b/drivers/dma/dmaengine.c > @@ -186,10 +186,9 @@ static void dma_client_chan_alloc(struct dma_client > *client) > /* we are done once this client rejects > * an available resource > */ > - if (ack == DMA_ACK) { > + if (ack == DMA_ACK) > dma_chan_get(chan); > - kref_get(&device->refcount); > - } else if (ack == DMA_NAK) > + else if (ack == DMA_NAK) > return; > } > } > @@ -276,11 +275,8 @@ static void dma_clients_notify_removed(struct dma_chan > *chan) > /* client was holding resources for this channel so > * free it > */ > - if (ack == DMA_ACK) { > + if (ack == DMA_ACK) > dma_chan_put(chan); > - kref_put(&chan->device->refcount, > - dma_async_device_cleanup); > - } > } > > mutex_unlock(&dma_list_mutex); > @@ -320,11 +316,8 @@ void dma_async_client_unregister(struct dma_client > *client) > ack = client->event_callback(client, chan, > DMA_RESOURCE_REMOVED); > > - if (ack == DMA_ACK) { > + if (ack == DMA_ACK) > dma_chan_put(chan); > - kref_put(&chan->device->refcount, > - dma_async_device_cleanup); > - } > } > > list_del(&client->global_node); > @@ -401,6 +394,8 @@ int dma_async_device_register(struct dma_device *device) > goto err_out; > } > > + /* One for the channel, one of the class device */ > + kref_get(&device->refcount); > kref_get(&device->refcount); > kref_init(&chan->refcount); > chan->slow_ref = 0; > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to [EMAIL PROTECTED] > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
Thanks - when I get back in tomorrow morning I'll test this to see that it gets rid of the panic that I've been getting. sln -- ============================================== Mr. Shannon Nelson Parents can't afford to be squeamish. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/