Tony Chuang <yhchuang@xxxxxxxxxxx> 於 2019年7月8日 週一 下午3:23寫道： > > > Subject: [PATCH] rtw88/pci: Rearrange the memory usage for skb in RX ISR > > nit, "rtw88: pci:" would be better. Ok. > > > > When skb allocation fails and the "rx routine starvation" is hit, the > > function returns immediately without updating the RX ring. At this > > point, the RX ring may continue referencing an old skb which was already > > handed off to ieee80211_rx_irqsafe(). When it comes to be used again, > > bad things happen. > > > > This patch allocates a new skb first in RX ISR. If we don't have memory > > available, we discard the current frame, allowing the existing skb to be > > reused in the ring. Otherwise, we simplify the code flow and just hand > > over the RX-populated skb over to mac80211. > > > > In addition, to fixing the kernel crash, the RX routine should now > > generally behave better under low memory conditions. > > > > Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=204053 > > Signed-off-by: Jian-Hong Pan <jian-hong@xxxxxxxxxxxx> > > Reviewed-by: Daniel Drake <drake@xxxxxxxxxxxx> > > Cc: <stable@xxxxxxxxxxxxxxx> > > --- > > drivers/net/wireless/realtek/rtw88/pci.c | 28 +++++++++++------------- > > 1 file changed, 13 insertions(+), 15 deletions(-) > > > > diff --git a/drivers/net/wireless/realtek/rtw88/pci.c > > b/drivers/net/wireless/realtek/rtw88/pci.c > > index cfe05ba7280d..1bfc99ae6b84 100644 > > --- a/drivers/net/wireless/realtek/rtw88/pci.c > > +++ b/drivers/net/wireless/realtek/rtw88/pci.c > > @@ -786,6 +786,15 @@ static void rtw_pci_rx_isr(struct rtw_dev *rtwdev, > > struct rtw_pci *rtwpci, > > rx_desc = skb->data; > > chip->ops->query_rx_desc(rtwdev, rx_desc, &pkt_stat, &rx_status); > > > > + /* discard current skb if the new skb cannot be allocated as a > > + * new one in rx ring later > > + * */ > > nit, comment indentation. Thanks. I will fix this. > > + new = dev_alloc_skb(RTK_PCI_RX_BUF_SIZE); > > + if (WARN(!new, "rx routine starvation\n")) { > > + new = skb; > > + goto next_rp; > > + } > > + > > /* offset from rx_desc to payload */ > > pkt_offset = pkt_desc_sz + pkt_stat.drv_info_sz + > > pkt_stat.shift; > > @@ -803,25 +812,14 @@ static void rtw_pci_rx_isr(struct rtw_dev *rtwdev, > > struct rtw_pci *rtwpci, > > skb_put(skb, pkt_stat.pkt_len); > > skb_reserve(skb, pkt_offset); > > > > - /* alloc a smaller skb to mac80211 */ > > - new = dev_alloc_skb(pkt_stat.pkt_len); > > - if (!new) { > > - new = skb; > > - } else { > > - skb_put_data(new, skb->data, skb->len); > > - dev_kfree_skb_any(skb); > > - } > > I am not sure if it's fine to deliver every huge SKB to mac80211. > Because it will then be delivered to TCP/IP stack. > Hence I think either it should be tested to know if the performance > would be impacted or find out a more efficient way to send > smaller SKB to mac80211 stack. I remember network stack only processes the skb with(in) pointers (skb->data) and the skb->len for data part. It also checks real buffer boundary (head and end) of the skb to prevent memory overflow. Therefore, I think using the original skb is the most efficient way. If I misunderstand something, please point out. > > /* TODO: merge into rx.c */ > > rtw_rx_stats(rtwdev, pkt_stat.vif, skb); > > - memcpy(new->cb, &rx_status, sizeof(rx_status)); > > - ieee80211_rx_irqsafe(rtwdev->hw, new); > > + memcpy(skb->cb, &rx_status, sizeof(rx_status)); > > + ieee80211_rx_irqsafe(rtwdev->hw, skb); > > } > > > > - /* skb delivered to mac80211, alloc a new one in rx ring */ > > - new = dev_alloc_skb(RTK_PCI_RX_BUF_SIZE); > > - if (WARN(!new, "rx routine starvation\n")) > > - return; > > - > > +next_rp: > > + /* skb delivered to mac80211, attach the new one into rx ring */ > > ring->buf[cur_rp] = new; > > rtw_pci_reset_rx_desc(rtwdev, new, ring, cur_rp, buf_desc_sz); > > > > -- > > Yan-Hsuan
