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Commit 2ba05622 authored by Dan Williams's avatar Dan Williams
Browse files

dmaengine: provide a common 'issue_pending_all' implementation 



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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarDan Williams <dan.j.williams@intel.com>
parent bec08513

crypto/async_tx/async_tx.c

+0 −12
Original line number Diff line number Diff line
@@ -45,18 +45,6 @@ static DEFINE_SPINLOCK(async_tx_lock); 


static LIST_HEAD(async_tx_master_list);



/* async_tx_issue_pending_all - start all transactions on all channels */

void async_tx_issue_pending_all(void)

{

	struct dma_chan_ref *ref;



	rcu_read_lock();

	list_for_each_entry_rcu(ref, &async_tx_master_list, node)

		ref->chan->device->device_issue_pending(ref->chan);

	rcu_read_unlock();

}

EXPORT_SYMBOL_GPL(async_tx_issue_pending_all);



static void

free_dma_chan_ref(struct rcu_head *rcu)

{

drivers/dma/dmaengine.c

+24 −3
Original line number Diff line number Diff line
@@ -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);

include/linux/async_tx.h

+1 −1
Original line number Diff line number Diff line
@@ -59,7 +59,7 @@ enum async_tx_flags { 
};



#ifdef CONFIG_DMA_ENGINE

void async_tx_issue_pending_all(void);

#define async_tx_issue_pending_all dma_issue_pending_all

#ifdef CONFIG_ARCH_HAS_ASYNC_TX_FIND_CHANNEL

#include <asm/async_tx.h>

#else

include/linux/dmaengine.h

+1 −0
Original line number Diff line number Diff line
@@ -471,6 +471,7 @@ int dma_async_device_register(struct dma_device *device); 
void dma_async_device_unregister(struct dma_device *device);

void dma_run_dependencies(struct dma_async_tx_descriptor *tx);

struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type);

void dma_issue_pending_all(void);



/* --- Helper iov-locking functions --- */

net/core/dev.c

+1 −8
Original line number Diff line number Diff line
@@ -2635,14 +2635,7 @@ out: 
	 * There may not be any more sk_buffs coming right now, so push

	 * any pending DMA copies to hardware

	 */

	if (!cpus_empty(net_dma.channel_mask)) {

		int chan_idx;

		for_each_cpu_mask_nr(chan_idx, net_dma.channel_mask) {

			struct dma_chan *chan = net_dma.channels[chan_idx];

			if (chan)

				dma_async_memcpy_issue_pending(chan);

		}

	}

	dma_issue_pending_all();

#endif



	return;