From: Jian-Hong Pan <jian-hong@endlessm.com>
To: Tony Chuang <yhchuang@realtek.com>
Cc: Kalle Valo <kvalo@codeaurora.org>,
"David S . Miller" <davem@davemloft.net>,
"linux-wireless@vger.kernel.org" <linux-wireless@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux@endlessm.com" <linux@endlessm.com>,
Daniel Drake <drake@endlessm.com>,
"stable@vger.kernel.org" <stable@vger.kernel.org>
Subject: Re: [PATCH] rtw88/pci: Rearrange the memory usage for skb in RX ISR
Date: Mon, 8 Jul 2019 16:07:23 +0800 [thread overview]
Message-ID: <CAPpJ_eebQtL0y_j98J2T7m9g77A61SVtvD8qnNN42bV0dm4MLA@mail.gmail.com> (raw)
In-Reply-To: <F7CD281DE3E379468C6D07993EA72F84D1861A6D@RTITMBSVM04.realtek.com.tw>
Tony Chuang <yhchuang@realtek.com> 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@endlessm.com>
> > Reviewed-by: Daniel Drake <drake@endlessm.com>
> > Cc: <stable@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.
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
next prev parent reply other threads:[~2019-07-08 8:08 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-08 6:32 [PATCH] rtw88/pci: Rearrange the memory usage for skb in RX ISR Jian-Hong Pan
2019-07-08 7:23 ` Tony Chuang
2019-07-08 8:07 ` Jian-Hong Pan [this message]
2019-07-08 9:00 ` Tony Chuang
2019-07-08 9:18 ` David Laight
2019-07-08 8:36 ` David Laight
2019-07-08 18:01 ` Larry Finger
2019-07-09 10:20 ` [PATCH v2 1/2] rtw88: pci: " Jian-Hong Pan
2019-07-10 8:36 ` Tony Chuang
2019-07-10 8:54 ` Jian-Hong Pan
2019-07-09 10:21 ` [PATCH v2 2/2] rtw88: pci: Use DMA sync instead of remapping " Jian-Hong Pan
2019-07-09 16:15 ` Christoph Hellwig
2019-07-10 8:38 ` [PATCH v3 1/2] rtw88: pci: Rearrange the memory usage for skb " Jian-Hong Pan
2019-07-10 8:57 ` David Laight
2019-07-11 3:50 ` Jian-Hong Pan
2019-07-11 5:24 ` [PATCH v4 " Jian-Hong Pan
2019-07-11 5:24 ` [PATCH v4 2/2] rtw88: pci: Use DMA sync instead of remapping " Jian-Hong Pan
2019-07-11 5:30 ` Jian-Hong Pan
2019-07-11 5:28 ` [PATCH v4 1/2] rtw88: pci: Rearrange the memory usage for skb " Jian-Hong Pan
2019-07-24 6:13 ` Jian-Hong Pan
2019-07-24 11:49 ` Kalle Valo
2019-08-15 20:25 ` [PATCH v3 " Brian Norris
2019-07-10 8:38 ` [PATCH v3 2/2] rtw88: pci: Use DMA sync instead of remapping " Jian-Hong Pan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAPpJ_eebQtL0y_j98J2T7m9g77A61SVtvD8qnNN42bV0dm4MLA@mail.gmail.com \
--to=jian-hong@endlessm.com \
--cc=davem@davemloft.net \
--cc=drake@endlessm.com \
--cc=kvalo@codeaurora.org \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-wireless@vger.kernel.org \
--cc=linux@endlessm.com \
--cc=netdev@vger.kernel.org \
--cc=stable@vger.kernel.org \
--cc=yhchuang@realtek.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).