linux-kernel - Re: [PATCH v4 1/2] rtw88: pci: Rearrange the memory usage for skb in RX ISR

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Message-Id: <20190724114940.4436E6053D@smtp.codeaurora.org>
Date:   Wed, 24 Jul 2019 11:49:40 +0000 (UTC)
From:   Kalle Valo <kvalo@...eaurora.org>
To:     Jian-Hong Pan <jian-hong@...lessm.com>
Cc:     Yan-Hsuan Chuang <yhchuang@...ltek.com>,
        "David S . Miller" <davem@...emloft.net>,
        Larry Finger <Larry.Finger@...inger.net>,
        David Laight <David.Laight@...lab.com>,
        Christoph Hellwig <hch@...radead.org>,
        linux-wireless@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux@...lessm.com,
        Daniel Drake <drake@...lessm.com>,
        Jian-Hong Pan <jian-hong@...lessm.com>, stable@...r.kernel.org
Subject: Re: [PATCH v4 1/2] rtw88: pci: Rearrange the memory usage for skb in
 RX ISR

Jian-Hong Pan <jian-hong@...lessm.com> wrote:

> 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, 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@...lessm.com>
> Cc: <stable@...r.kernel.org>

2 patches applied to wireless-drivers-next.git, thanks.

ee6db78f5db9 rtw88: pci: Rearrange the memory usage for skb in RX ISR
29b68a920f6a rtw88: pci: Use DMA sync instead of remapping in RX ISR

-- 
https://patchwork.kernel.org/patch/11039275/

https://wireless.wiki.kernel.org/en/developers/documentation/submittingpatches