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  1. 26 10月, 2019 2 次提交
    • V
      net: sch_generic: Use pfifo_fast as fallback scheduler for CAN hardware · 546b85bb
      由 Vincent Prince 提交于 
      There is networking hardware that isn't based on Ethernet for layers 1 and 2.

For example CAN.

CAN is a multi-master serial bus standard for connecting Electronic Control
Units [ECUs] also known as nodes. A frame on the CAN bus carries up to 8 bytes
of payload. Frame corruption is detected by a CRC. However frame loss due to
corruption is possible, but a quite unusual phenomenon.

While fq_codel works great for TCP/IP, it doesn't for CAN. There are a lot of
legacy protocols on top of CAN, which are not build with flow control or high
CAN frame drop rates in mind.

When using fq_codel, as soon as the queue reaches a certain delay based length,
skbs from the head of the queue are silently dropped. Silently meaning that the
user space using a send() or similar syscall doesn't get an error. However
TCP's flow control algorithm will detect dropped packages and adjust the
bandwidth accordingly.

When using fq_codel and sending raw frames over CAN, which is the common use
case, the user space thinks the package has been sent without problems, because
send() returned without an error. pfifo_fast will drop skbs, if the queue
length exceeds the maximum. But with this scheduler the skbs at the tail are
dropped, an error (-ENOBUFS) is propagated to user space. So that the user
space can slow down the package generation.

On distributions, where fq_codel is made default via CONFIG_DEFAULT_NET_SCH
during compile time, or set default during runtime with sysctl
net.core.default_qdisc (see [1]), we get a bad user experience. In my test case
with pfifo_fast, I can transfer thousands of million CAN frames without a frame
drop. On the other hand with fq_codel there is more then one lost CAN frame per
thousand frames.

As pointed out fq_codel is not suited for CAN hardware, so this patch changes
attach_one_default_qdisc() to use pfifo_fast for "ARPHRD_CAN" network devices.

During transition of a netdev from down to up state the default queuing
discipline is attached by attach_default_qdiscs() with the help of
attach_one_default_qdisc(). This patch modifies attach_one_default_qdisc() to
attach the pfifo_fast (pfifo_fast_ops) if the network device type is
"ARPHRD_CAN".

[1] https://github.com/systemd/systemd/issues/9194Suggested-by: NMarc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: NMarc Kleine-Budde <mkl@pengutronix.de>
Signed-off-by: NVincent Prince <vincent.prince.fr@gmail.com>
Acked-by: NDave Taht <dave.taht@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      546b85bb
    • H
      r8152: check the pointer rtl_fw->fw before using it · 8e484ebb
      由 Hayes Wang 提交于 
      Fix the pointer rtl_fw->fw would be used before checking in
rtl8152_apply_firmware() that causes the following kernel oops.

Unable to handle kernel NULL pointer dereference at virtual address 00000002
pgd = (ptrval)
[00000002] *pgd=00000000
Internal error: Oops: 5 [#1] PREEMPT SMP ARM
Modules linked in:
CPU: 0 PID: 131 Comm: kworker/0:2 Not tainted
5.4.0-rc1-00539-g9370f2d0 #6788
Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
Workqueue: events_long rtl_hw_phy_work_func_t
PC is at rtl8152_apply_firmware+0x14/0x464
LR is at r8153_hw_phy_cfg+0x24/0x17c
pc : [<c064f4e4>]    lr : [<c064fa18>]    psr: a0000013
sp : e75c9e60  ip : 60000013  fp : c11b7614
r10: e883b91c  r9 : 00000000  r8 : fffffffe
r7 : e883b640  r6 : fffffffe  r5 : fffffffe  r4 : e883b640
r3 : 736cfe7c  r2 : 736cfe7c  r1 : 000052f8  r0 : e883b640
Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
Control: 10c5387d  Table: 6640006a  DAC: 00000051
Process kworker/0:2 (pid: 131, stack limit = 0x(ptrval))
Stack: (0xe75c9e60 to 0xe75ca000)
...
[<c064f4e4>] (rtl8152_apply_firmware) from [<c064fa18>]
(r8153_hw_phy_cfg+0x24/0x17c)
[<c064fa18>] (r8153_hw_phy_cfg) from [<c064e784>]
(rtl_hw_phy_work_func_t+0x220/0x3e4)
[<c064e784>] (rtl_hw_phy_work_func_t) from [<c0148a74>]
(process_one_work+0x22c/0x7c8)
[<c0148a74>] (process_one_work) from [<c0149054>] (worker_thread+0x44/0x520)
[<c0149054>] (worker_thread) from [<c0150548>] (kthread+0x130/0x164)
[<c0150548>] (kthread) from [<c01010b4>] (ret_from_fork+0x14/0x20)
Exception stack(0xe75c9fb0 to 0xe75c9ff8)
...

Fixes: 9370f2d0 ("r8152: support request_firmware for RTL8153")
Reported-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Tested-by: NMarek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: NHayes Wang <hayeswang@realtek.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
      8e484ebb
  3. 25 10月, 2019 21 次提交
  5. 24 10月, 2019 9 次提交
  7. 23 10月, 2019 8 次提交