From: Logan Gunthorpe <logang@deltatee.com>
To: linux-kernel@vger.kernel.org, dmaengine@vger.kernel.org,
Vinod Koul <vkoul@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>,
Dave Jiang <dave.jiang@intel.com>, Kit Chow <kchow@gigaio.com>,
Logan Gunthorpe <logang@deltatee.com>
Subject: [PATCH 1/5] dmaengine: Store module owner in dma_device struct
Date: Mon, 16 Dec 2019 12:01:16 -0700 [thread overview]
Message-ID: <20191216190120.21374-2-logang@deltatee.com> (raw)
In-Reply-To: <20191216190120.21374-1-logang@deltatee.com>
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>
---
drivers/dma/dmaengine.c | 4 +++-
include/linux/dmaengine.h | 2 ++
2 files changed, 5 insertions(+), 1 deletion(-)
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 8fcdee1c0cf9..13aa0abb71de 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;
--
2.20.1
next prev parent reply other threads:[~2019-12-16 19:01 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-16 19:01 [PATCH 0/5] Support hot-unbind in IOAT Logan Gunthorpe
2019-12-16 19:01 ` Logan Gunthorpe [this message]
2019-12-16 19:01 ` [PATCH 2/5] dmaengine: Call module_put() after device_free_chan_resources() Logan Gunthorpe
2019-12-24 4:37 ` Vinod Koul
2019-12-16 19:01 ` [PATCH 3/5] dmaengine: Move dma_channel_rebalance() infrastructure up in code Logan Gunthorpe
2019-12-16 19:01 ` [PATCH 4/5] dmaengine: Add reference counting to dma_device struct Logan Gunthorpe
2019-12-16 19:01 ` [PATCH 5/5] dmaengine: ioat: Support in-use unbind Logan Gunthorpe
2019-12-17 16:33 ` Dave Jiang
2019-12-24 4:50 ` [PATCH 0/5] Support hot-unbind in IOAT Vinod Koul
2019-12-25 2:25 ` Logan Gunthorpe
-- strict thread matches above, loose matches on Subject: below --
2019-10-22 21:46 [PATCH 0/5] PLX Switch DMA Engine Driver Logan Gunthorpe
2019-10-22 21:46 ` [PATCH 1/5] dmaengine: Store module owner in dma_device struct Logan Gunthorpe
2019-11-09 17:18 ` Vinod Koul
2019-11-11 16:50 ` Logan Gunthorpe
2019-11-12 5:56 ` Vinod Koul
2019-11-12 16:45 ` Logan Gunthorpe
2019-11-14 4:55 ` Vinod Koul
2019-11-14 17:03 ` Logan Gunthorpe
2019-11-22 5:20 ` Vinod Koul
2019-11-22 16:53 ` Dave Jiang
2019-11-22 20:50 ` Dan Williams
2019-11-22 20:56 ` Logan Gunthorpe
2019-11-22 21:01 ` Dan Williams
2019-11-22 21:42 ` Dave Jiang
2019-12-10 9:53 ` Vinod Koul
2019-12-10 17:39 ` Logan Gunthorpe
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