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dmaengine: provide a common 'issue_pending_all' implementation

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async_tx and net_dma each have open-coded versions of issue_pending_all,
so provide a common routine in dmaengine.

The implementation needs to walk the global device list, so implement
rcu to allow dma_issue_pending_all to run lockless.  Clients protect
themselves from channel removal events by holding a dmaengine reference.

Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
This commit is contained in:
Dan Williams
2009-01-06 11:38:14 -07:00
parent bec085134e
commit 2ba05622b8
5 changed files with 27 additions and 24 deletions
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27
drivers/dma/dmaengine.c
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@@ -70,6 +70,7 @@
#include <linux/rcupdate.h>
#include <linux/mutex.h>
#include <linux/jiffies.h>
#include <linux/rculist.h>
static DEFINE_MUTEX(dma_list_mutex);
static LIST_HEAD(dma_device_list);
@@ -365,6 +366,26 @@ struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type)
}
EXPORT_SYMBOL(dma_find_channel);
/**
* dma_issue_pending_all - flush all pending operations across all channels
*/
void dma_issue_pending_all(void)
{
struct dma_device *device;
struct dma_chan *chan;
WARN_ONCE(dmaengine_ref_count == 0,
"client called %s without a reference", __func__);
rcu_read_lock();
list_for_each_entry_rcu(device, &dma_device_list, global_node)
list_for_each_entry(chan, &device->channels, device_node)
if (chan->client_count)
device->device_issue_pending(chan);
rcu_read_unlock();
}
EXPORT_SYMBOL(dma_issue_pending_all);
/**
* nth_chan - returns the nth channel of the given capability
* @cap: capability to match
@@ -490,7 +511,7 @@ void dma_async_client_register(struct dma_client *client)
err = dma_chan_get(chan);
if (err == -ENODEV) {
/* module removed before we could use it */
list_del_init(&device->global_node);
list_del_rcu(&device->global_node);
break;
} else if (err)
pr_err("dmaengine: failed to get %s: (%d)\n",
@@ -635,7 +656,7 @@ int dma_async_device_register(struct dma_device *device)
goto err_out;
}
}
list_add_tail(&device->global_node, &dma_device_list);
list_add_tail_rcu(&device->global_node, &dma_device_list);
dma_channel_rebalance();
mutex_unlock(&dma_list_mutex);
@@ -677,7 +698,7 @@ void dma_async_device_unregister(struct dma_device *device)
struct dma_chan *chan;
mutex_lock(&dma_list_mutex);
list_del(&device->global_node);
list_del_rcu(&device->global_node);
dma_channel_rebalance();
mutex_unlock(&dma_list_mutex);