diff options
author | Logan Gunthorpe <logang@deltatee.com> | 2019-12-16 12:01:19 -0700 |
---|---|---|
committer | Vinod Koul <vkoul@kernel.org> | 2019-12-24 10:18:32 +0530 |
commit | 8ad342a863590b24ce77681b7e081363fb3333f7 (patch) | |
tree | 393b6621b115e7cc07ff47e75ab897f929902654 /drivers/dma/dmaengine.c | |
parent | 11a0fd2b3baa5e4a97197b9cd990b5d05e69d669 (diff) |
dmaengine: Add reference counting to dma_device struct
Adding a reference count helps drivers to properly implement the unbind
while in use case.
References are taken and put every time a channel is allocated or freed.
Once the final reference is put, the device is removed from the
dma_device_list and a release callback function is called to signal
the driver to free the memory.
Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Link: https://lore.kernel.org/r/20191216190120.21374-5-logang@deltatee.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Diffstat (limited to 'drivers/dma/dmaengine.c')
-rw-r--r-- | drivers/dma/dmaengine.c | 57 |
1 files changed, 49 insertions, 8 deletions
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c index 1f9a6293f15a..e316abe3672d 100644 --- a/drivers/dma/dmaengine.c +++ b/drivers/dma/dmaengine.c @@ -342,6 +342,23 @@ static void balance_ref_count(struct dma_chan *chan) } } +static void dma_device_release(struct kref *ref) +{ + struct dma_device *device = container_of(ref, struct dma_device, ref); + + list_del_rcu(&device->global_node); + dma_channel_rebalance(); + + if (device->device_release) + device->device_release(device); +} + +static void dma_device_put(struct dma_device *device) +{ + lockdep_assert_held(&dma_list_mutex); + kref_put(&device->ref, dma_device_release); +} + /** * dma_chan_get - try to grab a dma channel's parent driver module * @chan - channel to grab @@ -362,6 +379,12 @@ static int dma_chan_get(struct dma_chan *chan) if (!try_module_get(owner)) return -ENODEV; + ret = kref_get_unless_zero(&chan->device->ref); + if (!ret) { + ret = -ENODEV; + goto module_put_out; + } + /* allocate upon first client reference */ if (chan->device->device_alloc_chan_resources) { ret = chan->device->device_alloc_chan_resources(chan); @@ -377,6 +400,8 @@ out: return 0; err_out: + dma_device_put(chan->device); +module_put_out: module_put(owner); return ret; } @@ -402,6 +427,7 @@ static void dma_chan_put(struct dma_chan *chan) chan->device->device_free_chan_resources(chan); } + dma_device_put(chan->device); module_put(dma_chan_to_owner(chan)); /* If the channel is used via a DMA request router, free the mapping */ @@ -837,14 +863,14 @@ EXPORT_SYMBOL(dmaengine_get); */ void dmaengine_put(void) { - struct dma_device *device; + struct dma_device *device, *_d; struct dma_chan *chan; mutex_lock(&dma_list_mutex); dmaengine_ref_count--; BUG_ON(dmaengine_ref_count < 0); /* drop channel references */ - list_for_each_entry(device, &dma_device_list, global_node) { + list_for_each_entry_safe(device, _d, &dma_device_list, global_node) { if (dma_has_cap(DMA_PRIVATE, device->cap_mask)) continue; list_for_each_entry(chan, &device->channels, device_node) @@ -906,6 +932,10 @@ static int get_dma_id(struct dma_device *device) /** * dma_async_device_register - registers DMA devices found * @device: &dma_device + * + * After calling this routine the structure should not be freed except in the + * device_release() callback which will be called after + * dma_async_device_unregister() is called and no further references are taken. */ int dma_async_device_register(struct dma_device *device) { @@ -999,6 +1029,12 @@ int dma_async_device_register(struct dma_device *device) return -EIO; } + if (!device->device_release) + dev_warn(device->dev, + "WARN: Device release is not defined so it is not safe to unbind this driver while in use\n"); + + kref_init(&device->ref); + /* note: this only matters in the * CONFIG_ASYNC_TX_ENABLE_CHANNEL_SWITCH=n case */ @@ -1115,13 +1151,8 @@ void dma_async_device_unregister(struct dma_device *device) { struct dma_chan *chan; - mutex_lock(&dma_list_mutex); - list_del_rcu(&device->global_node); - dma_channel_rebalance(); - mutex_unlock(&dma_list_mutex); - list_for_each_entry(chan, &device->channels, device_node) { - WARN_ONCE(chan->client_count, + WARN_ONCE(!device->device_release && chan->client_count, "%s called while %d clients hold a reference\n", __func__, chan->client_count); mutex_lock(&dma_list_mutex); @@ -1130,6 +1161,16 @@ void dma_async_device_unregister(struct dma_device *device) device_unregister(&chan->dev->device); free_percpu(chan->local); } + + mutex_lock(&dma_list_mutex); + /* + * setting DMA_PRIVATE ensures the device being torn down will not + * be used in the channel_table + */ + dma_cap_set(DMA_PRIVATE, device->cap_mask); + dma_channel_rebalance(); + dma_device_put(device); + mutex_unlock(&dma_list_mutex); } EXPORT_SYMBOL(dma_async_device_unregister); |