From: Jian-Hong Pan > Sent: 10 July 2019 09:38 > > Testing with RTL8822BE hardware, when available memory is low, we > frequently see a kernel panic and system freeze. > > First, rtw_pci_rx_isr encounters a memory allocation failure (trimmed): > > rx routine starvation > WARNING: CPU: 7 PID: 9871 at drivers/net/wireless/realtek/rtw88/pci.c:822 > rtw_pci_rx_isr.constprop.25+0x35a/0x370 [rtwpci] > [ 2356.580313] RIP: 0010:rtw_pci_rx_isr.constprop.25+0x35a/0x370 [rtwpci] > > Then we see a variety of different error conditions and kernel panics, > such as this one (trimmed): > > rtw_pci 0000:02:00.0: pci bus timeout, check dma status > skbuff: skb_over_panic: text:00000000091b6e66 len:415 put:415 head:00000000d2880c6f > data:000000007a02b1ea tail:0x1df end:0xc0 dev:<NULL> > ------------[ cut here ]------------ > kernel BUG at net/core/skbuff.c:105! > invalid opcode: 0000 [#1] SMP NOPTI > RIP: 0010:skb_panic+0x43/0x45 > > 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, data-sized skb first in RX ISR. After > copying the data in, we pass it to the upper layers. However, if skb > allocation fails, we effectively drop the frame. In both cases, the > original, full size ring skb is reused. > > In addition, by fixing the kernel crash, the RX routine should now > generally behave better under low memory conditions. A couple of minor nits (see below). You may want to do a followup patch that changes the rx buffers (used by the hardware) to by just memory buffers. Nothing (probably) relies on them being skb with all the accociated baggage. David > > Buglink: https://bugzilla.kernel.org/show_bug.cgi?id=204053 > Signed-off-by: Jian-Hong Pan <jian-hong@xxxxxxxxxxxx> > Cc: <stable@xxxxxxxxxxxxxxx> > --- > v2: > - Allocate new data-sized skb and put data into it, then pass it to > mac80211. Reuse the original skb in RX ring by DMA sync. > - Modify the commit message. > - Introduce following [PATCH v3 2/2] rtw88: pci: Use DMA sync instead > of remapping in RX ISR. > > v3: > - Same as v2. > > drivers/net/wireless/realtek/rtw88/pci.c | 49 +++++++++++------------- > 1 file changed, 22 insertions(+), 27 deletions(-) > > diff --git a/drivers/net/wireless/realtek/rtw88/pci.c b/drivers/net/wireless/realtek/rtw88/pci.c > index cfe05ba7280d..e9fe3ad896c8 100644 > --- a/drivers/net/wireless/realtek/rtw88/pci.c > +++ b/drivers/net/wireless/realtek/rtw88/pci.c > @@ -763,6 +763,7 @@ static void rtw_pci_rx_isr(struct rtw_dev *rtwdev, struct rtw_pci *rtwpci, > u32 pkt_offset; > u32 pkt_desc_sz = chip->rx_pkt_desc_sz; > u32 buf_desc_sz = chip->rx_buf_desc_sz; > + u32 new_len; > u8 *rx_desc; > dma_addr_t dma; > > @@ -790,40 +791,34 @@ static void rtw_pci_rx_isr(struct rtw_dev *rtwdev, struct rtw_pci *rtwpci, > pkt_offset = pkt_desc_sz + pkt_stat.drv_info_sz + > pkt_stat.shift; > > - if (pkt_stat.is_c2h) { > - /* keep rx_desc, halmac needs it */ > - skb_put(skb, pkt_stat.pkt_len + pkt_offset); > + /* discard current skb if the new skb cannot be allocated as a > + * new one in rx ring later > + */ That comment isn't quite right. maybe: "Allocate a new skb for this frame, discard if none available" > + new_len = pkt_stat.pkt_len + pkt_offset; > + new = dev_alloc_skb(new_len); > + if (WARN_ONCE(!new, "rx routine starvation\n")) I think you should count these?? > + goto next_rp; > + > + /* put the DMA data including rx_desc from phy to new skb */ > + skb_put_data(new, skb->data, new_len); > > - /* pass offset for further operation */ > - *((u32 *)skb->cb) = pkt_offset; > - skb_queue_tail(&rtwdev->c2h_queue, skb); > + if (pkt_stat.is_c2h) { > + /* pass rx_desc & offset for further operation */ > + *((u32 *)new->cb) = pkt_offset; > + skb_queue_tail(&rtwdev->c2h_queue, new); > ieee80211_queue_work(rtwdev->hw, &rtwdev->c2h_work); > } else { > - /* remove rx_desc, maybe use skb_pull? */ > - 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); > - } > - /* TODO: merge into rx.c */ > - rtw_rx_stats(rtwdev, pkt_stat.vif, skb); > + /* remove rx_desc */ > + skb_pull(new, pkt_offset); > + > + rtw_rx_stats(rtwdev, pkt_stat.vif, new); > memcpy(new->cb, &rx_status, sizeof(rx_status)); > ieee80211_rx_irqsafe(rtwdev->hw, new); > } > > - /* 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; > - > - ring->buf[cur_rp] = new; > - rtw_pci_reset_rx_desc(rtwdev, new, ring, cur_rp, buf_desc_sz); > +next_rp: > + /* new skb delivered to mac80211, re-enable original skb DMA */ > + rtw_pci_reset_rx_desc(rtwdev, skb, ring, cur_rp, buf_desc_sz); > > /* host read next element in ring */ > if (++cur_rp >= ring->r.len) > -- > 2.22.0 - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
