diff options
| author | Logan Gunthorpe <logang@deltatee.com> | 2019-12-16 12:01:16 -0700 |
|---|---|---|
| committer | Vinod Koul <vkoul@kernel.org> | 2019-12-24 10:18:32 +0530 |
| commit | dae7a589c18a4d979d5f14b09374e871b995ceb1 (patch) | |
| tree | b788a32e2ed73ecd8fbe3961f95456b2b9dc66e9 | |
| parent | 20f5a659554a6e684da0806939bddf8f6537e936 (diff) | |
dmaengine: Store module owner in dma_device struct
dma_chan_to_owner() dereferences the driver from the struct device to
obtain the owner and call module_[get|put](). However, if the backing
device is unbound before the dma_device is unregistered, the driver
will be cleared and this will cause a NULL pointer dereference.
Instead, store a pointer to the owner module in the dma_device struct
so the module reference can be properly put when the channel is put, even
if the backing device was destroyed first.
This change helps to support a safer unbind of DMA engines.
If the dma_device is unregistered in the driver's remove function,
there's no guarantee that there are no existing clients and a users
action may trigger the WARN_ONCE in dma_async_device_unregister()
which is unlikely to leave the system in a consistent state.
Instead, a better approach is to allow the backing driver to go away
and fail any subsequent requests to it.
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Link: https://lore.kernel.org/r/20191216190120.21374-2-logang@deltatee.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
| -rw-r--r-- | drivers/dma/dmaengine.c | 4 | ||||
| -rw-r--r-- | include/linux/dmaengine.h | 2 |
2 files changed, 5 insertions, 1 deletions
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c index 03ac4b96117c..4b604086b1b3 100644 --- a/drivers/dma/dmaengine.c +++ b/drivers/dma/dmaengine.c @@ -179,7 +179,7 @@ __dma_device_satisfies_mask(struct dma_device *device, static struct module *dma_chan_to_owner(struct dma_chan *chan) { - return chan->device->dev->driver->owner; + return chan->device->owner; } /** @@ -919,6 +919,8 @@ int dma_async_device_register(struct dma_device *device) return -EIO; } + device->owner = device->dev->driver->owner; + if (dma_has_cap(DMA_MEMCPY, device->cap_mask) && !device->device_prep_dma_memcpy) { dev_err(device->dev, "Device claims capability %s, but op is not defined\n", diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h index dfd2d35b64af..11b15a2e97a0 100644 --- a/include/linux/dmaengine.h +++ b/include/linux/dmaengine.h @@ -674,6 +674,7 @@ struct dma_filter { * @fill_align: alignment shift for memset operations * @dev_id: unique device ID * @dev: struct device reference for dma mapping api + * @owner: owner module (automatically set based on the provided dev) * @src_addr_widths: bit mask of src addr widths the device supports * Width is specified in bytes, e.g. for a device supporting * a width of 4 the mask should have BIT(4) set. @@ -737,6 +738,7 @@ struct dma_device { int dev_id; struct device *dev; + struct module *owner; u32 src_addr_widths; u32 dst_addr_widths; |