There are cases where we can use this_cpu_ptr and as the result of using this_cpu_ptr() we no longer need to determine the currently executing cpu. In those places no get/put_cpu combination is needed anymore. The local cpu variable can be eliminated. Preemption still needs to be disabled and enabled since the modifications of the per cpu variables is not atomic. There may be multiple per cpu variables modified and those must all be from the same processor. Acked-by: Maciej Sosnowski Acked-by: Dan Williams Acked-by: Tejun Heo cc: Eric Biederman cc: Stephen Hemminger cc: David L Stevens Signed-off-by: Christoph Lameter --- drivers/dma/dmaengine.c | 36 +++++++++++++----------------------- drivers/net/veth.c | 7 +++---- 2 files changed, 16 insertions(+), 27 deletions(-) Index: linux-2.6/drivers/dma/dmaengine.c =================================================================== --- linux-2.6.orig/drivers/dma/dmaengine.c 2009-09-28 10:08:09.000000000 -0500 +++ linux-2.6/drivers/dma/dmaengine.c 2009-09-29 09:01:54.000000000 -0500 @@ -326,14 +326,7 @@ arch_initcall(dma_channel_table_init); */ struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type) { - struct dma_chan *chan; - int cpu; - - cpu = get_cpu(); - chan = per_cpu_ptr(channel_table[tx_type], cpu)->chan; - put_cpu(); - - return chan; + return this_cpu_read(channel_table[tx_type]->chan); } EXPORT_SYMBOL(dma_find_channel); @@ -847,7 +840,6 @@ dma_async_memcpy_buf_to_buf(struct dma_c struct dma_async_tx_descriptor *tx; dma_addr_t dma_dest, dma_src; dma_cookie_t cookie; - int cpu; unsigned long flags; dma_src = dma_map_single(dev->dev, src, len, DMA_TO_DEVICE); @@ -866,10 +858,10 @@ dma_async_memcpy_buf_to_buf(struct dma_c tx->callback = NULL; cookie = tx->tx_submit(tx); - cpu = get_cpu(); - per_cpu_ptr(chan->local, cpu)->bytes_transferred += len; - per_cpu_ptr(chan->local, cpu)->memcpy_count++; - put_cpu(); + preempt_disable(); + __this_cpu_add(chan->local->bytes_transferred, len); + __this_cpu_inc(chan->local->memcpy_count); + preempt_enable(); return cookie; } @@ -896,7 +888,6 @@ dma_async_memcpy_buf_to_pg(struct dma_ch struct dma_async_tx_descriptor *tx; dma_addr_t dma_dest, dma_src; dma_cookie_t cookie; - int cpu; unsigned long flags; dma_src = dma_map_single(dev->dev, kdata, len, DMA_TO_DEVICE); @@ -913,10 +904,10 @@ dma_async_memcpy_buf_to_pg(struct dma_ch tx->callback = NULL; cookie = tx->tx_submit(tx); - cpu = get_cpu(); - per_cpu_ptr(chan->local, cpu)->bytes_transferred += len; - per_cpu_ptr(chan->local, cpu)->memcpy_count++; - put_cpu(); + preempt_disable(); + __this_cpu_add(chan->local->bytes_transferred, len); + __this_cpu_inc(chan->local->memcpy_count); + preempt_enable(); return cookie; } @@ -945,7 +936,6 @@ dma_async_memcpy_pg_to_pg(struct dma_cha struct dma_async_tx_descriptor *tx; dma_addr_t dma_dest, dma_src; dma_cookie_t cookie; - int cpu; unsigned long flags; dma_src = dma_map_page(dev->dev, src_pg, src_off, len, DMA_TO_DEVICE); @@ -963,10 +953,10 @@ dma_async_memcpy_pg_to_pg(struct dma_cha tx->callback = NULL; cookie = tx->tx_submit(tx); - cpu = get_cpu(); - per_cpu_ptr(chan->local, cpu)->bytes_transferred += len; - per_cpu_ptr(chan->local, cpu)->memcpy_count++; - put_cpu(); + preempt_disable(); + __this_cpu_add(chan->local->bytes_transferred, len); + __this_cpu_inc(chan->local->memcpy_count); + preempt_enable(); return cookie; } Index: linux-2.6/drivers/net/veth.c =================================================================== --- linux-2.6.orig/drivers/net/veth.c 2009-09-17 17:54:16.000000000 -0500 +++ linux-2.6/drivers/net/veth.c 2009-09-29 09:01:54.000000000 -0500 @@ -153,7 +153,7 @@ static netdev_tx_t veth_xmit(struct sk_b struct net_device *rcv = NULL; struct veth_priv *priv, *rcv_priv; struct veth_net_stats *stats, *rcv_stats; - int length, cpu; + int length; skb_orphan(skb); @@ -161,9 +161,8 @@ static netdev_tx_t veth_xmit(struct sk_b rcv = priv->peer; rcv_priv = netdev_priv(rcv); - cpu = smp_processor_id(); - stats = per_cpu_ptr(priv->stats, cpu); - rcv_stats = per_cpu_ptr(rcv_priv->stats, cpu); + stats = this_cpu_ptr(priv->stats); + rcv_stats = this_cpu_ptr(rcv_priv->stats); if (!(rcv->flags & IFF_UP)) goto tx_drop; -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/