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Date: Fri, 14 Nov 2008 14:34:42 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Cc: maciej.sosnowski@...el.com, hskinnemoen@...el.com,
g.liakhovetski@....de, nicolas.ferre@...el.com
Subject: [PATCH 05/13] 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.
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
crypto/async_tx/async_tx.c | 12 ------------
drivers/dma/dmaengine.c | 27 ++++++++++++++++++++++++---
include/linux/async_tx.h | 2 +-
include/linux/dmaengine.h | 1 +
net/core/dev.c | 9 +--------
5 files changed, 27 insertions(+), 24 deletions(-)
diff --git a/crypto/async_tx/async_tx.c b/crypto/async_tx/async_tx.c
index b88bb1f..2cdf7a0 100644
--- a/crypto/async_tx/async_tx.c
+++ b/crypto/async_tx/async_tx.c
@@ -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)
{
diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
index c3e6fbb..ec483cc 100644
--- a/drivers/dma/dmaengine.c
+++ b/drivers/dma/dmaengine.c
@@ -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);
@@ -354,6 +355,26 @@ 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
* @n: nth channel desired
@@ -477,7 +498,7 @@ 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)",
@@ -612,7 +633,7 @@ 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);
@@ -654,7 +675,7 @@ 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);
diff --git a/include/linux/async_tx.h b/include/linux/async_tx.h
index 1c81677..45f6297 100644
--- a/include/linux/async_tx.h
+++ b/include/linux/async_tx.h
@@ -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
diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
index b466f02..57a43ad 100644
--- a/include/linux/dmaengine.h
+++ b/include/linux/dmaengine.h
@@ -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 --- */
diff --git a/net/core/dev.c b/net/core/dev.c
index 9174c77..301a449 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2442,14 +2442,7 @@ 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;
--
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