From 751ae21c6cd1493e3d0a4935b08fb298b9d89773 Mon Sep 17 00:00:00 2001 From: Santiago Leon Date: Tue, 3 Oct 2006 12:24:45 -0500 Subject: [PATCH] [PATCH] ibmveth: fix int rollover panic This patch fixes a nasty bug that has been sitting there since the very first versions of the driver, but is generating a panic because we changed the number of 2K buffers for 2.6.16. The consumer_index and producer_index are u32's that get incremented on every buffer emptied and replenished respectively. We use the {producer,consumer}_index mod'ed with the size of the pool to pick out an entry in the free_map. The problem happens when the u32 rolls over and the number of the buffers in the pool is not a perfect divisor of 2^32. i.e. if the number of 2K buffers is 0x300, before the consumer_index rolls over, our index to the free map = 0xffffffff mod 0x300 = 0xff. The next time a buffer is emptied, we want the index to the free map to be 0x100, but 0x0 mod 0x300 is 0x0. This patch assigns the mod'ed result back to the consumer and producer indexes so that they never roll over. The second chunk of the patch covers the unlikely case where the consumer_index has just been reset to 0x0 and the hypervisor is not able to accept that buffer. Signed-off-by: Santiago Leon Signed-off-by: Jeff Garzik --- drivers/net/ibmveth.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/net/ibmveth.c b/drivers/net/ibmveth.c index 6aff2bc3df55..16f3faa7ea5b 100644 --- a/drivers/net/ibmveth.c +++ b/drivers/net/ibmveth.c @@ -213,6 +213,7 @@ static void ibmveth_replenish_buffer_pool(struct ibmveth_adapter *adapter, struc } free_index = pool->consumer_index++ % pool->size; + pool->consumer_index = free_index; index = pool->free_map[free_index]; ibmveth_assert(index != IBM_VETH_INVALID_MAP); @@ -238,7 +239,10 @@ static void ibmveth_replenish_buffer_pool(struct ibmveth_adapter *adapter, struc if(lpar_rc != H_SUCCESS) { pool->free_map[free_index] = index; pool->skbuff[index] = NULL; - pool->consumer_index--; + if (pool->consumer_index == 0) + pool->consumer_index = pool->size - 1; + else + pool->consumer_index--; dma_unmap_single(&adapter->vdev->dev, pool->dma_addr[index], pool->buff_size, DMA_FROM_DEVICE); @@ -326,6 +330,7 @@ static void ibmveth_remove_buffer_from_pool(struct ibmveth_adapter *adapter, u64 DMA_FROM_DEVICE); free_index = adapter->rx_buff_pool[pool].producer_index++ % adapter->rx_buff_pool[pool].size; + adapter->rx_buff_pool[pool].producer_index = free_index; adapter->rx_buff_pool[pool].free_map[free_index] = index; mb(); -- 2.20.1