Re: [PATCH] net: hns: avoid uninitialized variable warning:
From: Yisen Zhuang <hidden>
Date: 2016-01-06 00:56:27
Also in:
linux-arm-kernel, lkml
在 2016/1/2 6:27, Arnd Bergmann 写道:
gcc fails to see that the use of the 'last_offset' variable in hns_nic_reuse_page() is used correctly and issues a bogus warning: drivers/net/ethernet/hisilicon/hns/hns_enet.c: In function 'hns_nic_reuse_page': drivers/net/ethernet/hisilicon/hns/hns_enet.c:541:6: warning: 'last_offset' may be used uninitialized in this function [-Wmaybe-uninitialized] This simplifies the function to make it more obvious what is going on to both readers and compilers, which makes the warning go away.
Hi Arnd, This patch is fine to me. Many thanks, Yisen
quoted hunk ↗ jump to hunk
Signed-off-by: Arnd Bergmann <arnd@arndb.de> --- Compile-tested only, and complex enough that this requires a proper review and testing before it gets apply. Please have a look at this.diff --git a/drivers/net/ethernet/hisilicon/hns/hns_enet.c b/drivers/net/ethernet/hisilicon/hns/hns_enet.c index 5a81dafd725e..0e30846a24f8 100644 --- a/drivers/net/ethernet/hisilicon/hns/hns_enet.c +++ b/drivers/net/ethernet/hisilicon/hns/hns_enet.c@@ -499,50 +499,47 @@ static void hns_nic_reuse_page(struct sk_buff *skb, int i, struct hnae_desc *desc; int truesize, size; int last_offset; + bool twobufs; + + twobufs = ((PAGE_SIZE < 8192) && hnae_buf_size(ring) == HNS_BUFFER_SIZE_2048); desc = &ring->desc[ring->next_to_clean]; size = le16_to_cpu(desc->rx.size); -#if (PAGE_SIZE < 8192) - if (hnae_buf_size(ring) == HNS_BUFFER_SIZE_2048) { + if (twobufs) { truesize = hnae_buf_size(ring); } else { truesize = ALIGN(size, L1_CACHE_BYTES); last_offset = hnae_page_size(ring) - hnae_buf_size(ring); } -#else - truesize = ALIGN(size, L1_CACHE_BYTES); - last_offset = hnae_page_size(ring) - hnae_buf_size(ring); -#endif - skb_add_rx_frag(skb, i, desc_cb->priv, desc_cb->page_offset + pull_len, size - pull_len, truesize - pull_len); /* avoid re-using remote pages,flag default unreuse */ - if (likely(page_to_nid(desc_cb->priv) == numa_node_id())) { -#if (PAGE_SIZE < 8192) - if (hnae_buf_size(ring) == HNS_BUFFER_SIZE_2048) { - /* if we are only owner of page we can reuse it */ - if (likely(page_count(desc_cb->priv) == 1)) { - /* flip page offset to other buffer */ - desc_cb->page_offset ^= truesize; - - desc_cb->reuse_flag = 1; - /* bump ref count on page before it is given*/ - get_page(desc_cb->priv); - } - return; - } -#endif - /* move offset up to the next cache line */ - desc_cb->page_offset += truesize; + if (unlikely(page_to_nid(desc_cb->priv) != numa_node_id())) + return; + + if (twobufs) { + /* if we are only owner of page we can reuse it */ + if (likely(page_count(desc_cb->priv) == 1)) { + /* flip page offset to other buffer */ + desc_cb->page_offset ^= truesize; - if (desc_cb->page_offset <= last_offset) { desc_cb->reuse_flag = 1; /* bump ref count on page before it is given*/ get_page(desc_cb->priv); } + return; + } + + /* move offset up to the next cache line */ + desc_cb->page_offset += truesize; + + if (desc_cb->page_offset <= last_offset) { + desc_cb->reuse_flag = 1; + /* bump ref count on page before it is given*/ + get_page(desc_cb->priv); } }.