> Subject: [PATCH] rtw88/pci: Rearrange the memory usage for skb in RX ISR
nit, "rtw88: pci:" would be better. > > > 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-h...@endlessm.com> > Reviewed-by: Daniel Drake <dr...@endlessm.com> > Cc: <sta...@vger.kernel.org> > --- > 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. > + 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. > /* 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
