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authorDan Williams <dan.j.williams@intel.com>2009-01-06 11:38:14 -0700
committerDan Williams <dan.j.williams@intel.com>2009-01-06 11:38:14 -0700
commit6f49a57aa5a0c6d4e4e27c85f7af6c83325a12d1 (patch)
treeafba24357d1f4ff69ccb2b39a19542546590a50b /crypto
parent07f2211e4fbce6990722d78c4f04225da9c0e9cf (diff)
downloadconfigs-6f49a57aa5a0c6d4e4e27c85f7af6c83325a12d1.tar.gz
dmaengine: up-level reference counting to the module level
Simply, if a client wants any dmaengine channel then prevent all dmaengine modules from being removed. Once the clients are done re-enable module removal. Why?, beyond reducing complication: 1/ Tracking reference counts per-transaction in an efficient manner, as is currently done, requires a complicated scheme to avoid cache-line bouncing effects. 2/ Per-transaction ref-counting gives the false impression that a dma-driver can be gracefully removed ahead of its user (net, md, or dma-slave) 3/ None of the in-tree dma-drivers talk to hot pluggable hardware, but if such an engine were built one day we still would not need to notify clients of remove events. The driver can simply return NULL to a ->prep() request, something that is much easier for a client to handle. Reviewed-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Maciej Sosnowski <maciej.sosnowski@intel.com> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Diffstat (limited to 'crypto')
-rw-r--r--crypto/async_tx/async_tx.c4
1 files changed, 0 insertions, 4 deletions
diff --git a/crypto/async_tx/async_tx.c b/crypto/async_tx/async_tx.c
index 8cfac182165..43fe4cbe71e 100644
--- a/crypto/async_tx/async_tx.c
+++ b/crypto/async_tx/async_tx.c
@@ -198,8 +198,6 @@ dma_channel_add_remove(struct dma_client *client,
/* add the channel to the generic management list */
master_ref = kmalloc(sizeof(*master_ref), GFP_KERNEL);
if (master_ref) {
- /* keep a reference until async_tx is unloaded */
- dma_chan_get(chan);
init_dma_chan_ref(master_ref, chan);
spin_lock_irqsave(&async_tx_lock, flags);
list_add_tail_rcu(&master_ref->node,
@@ -221,8 +219,6 @@ dma_channel_add_remove(struct dma_client *client,
spin_lock_irqsave(&async_tx_lock, flags);
list_for_each_entry(ref, &async_tx_master_list, node)
if (ref->chan == chan) {
- /* permit backing devices to go away */
- dma_chan_put(ref->chan);
list_del_rcu(&ref->node);
call_rcu(&ref->rcu, free_dma_chan_ref);
found = 1;