netdev - Re: [PATCH net v2] net: phy: Correctly process PHY_HALTED in phy_stop

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Date:   Wed, 30 Aug 2017 17:13:52 -0700
From:   David Daney <ddaney.cavm@...il.com>
To:     David Miller <davem@...emloft.net>, f.fainelli@...il.com
Cc:     netdev@...r.kernel.org, andrew@...n.ch, slash.tmp@...e.fr,
        marc_gonzalez@...madesigns.com, rmk+kernel@...linux.org.uk
Subject: Re: [PATCH net v2] net: phy: Correctly process PHY_HALTED in
 phy_stop_machine()

On 07/31/2017 05:28 PM, David Miller wrote:
> From: Florian Fainelli <f.fainelli@...il.com>
> Date: Fri, 28 Jul 2017 11:58:36 -0700
> 
>> Marc reported that he was not getting the PHY library adjust_link()
>> callback function to run when calling phy_stop() + phy_disconnect()
>> which does not indeed happen because we set the state machine to
>> PHY_HALTED but we don't get to run it to process this state past that
>> point.
>>
>> Fix this with a synchronous call to phy_state_machine() in order to have
>> the state machine actually act on PHY_HALTED, set the PHY device's link
>> down, turn the network device's carrier off and finally call the
>> adjust_link() function.
>>
>> Reported-by: Marc Gonzalez <marc_gonzalez@...madesigns.com>
>> Fixes: a390d1f379cf ("phylib: convert state_queue work to delayed_work")
>> Signed-off-by: Florian Fainelli <f.fainelli@...il.com>
>> ---
>> Changes in v2:
>>
>> - reword subject and commit message based on changes
>> - dropped flush_scheduled_work() since it is redundant
> 
> Applied and queued up for -stable, thanks.
> 


This is broken.  Please revert.

Upstream commit 7ad813f20853 and in the stable branches as well.

When ndo_stop() is called we call:


  phy_disconnect()
     +---> phy_stop_interrupts() implies: phydev->irq = PHY_POLL;
     +---> phy_stop_machine()
     |      +---> phy_stop_machine()
     |              +----> queue_delayed_work(): Work queued.
     +--->phy_detach() implies: phydev->attached_dev = NULL;

Now at a later time the queued work does:

  phy_state_machine()
     +---->netif_carrier_off(phydev->attached_dev): Oh no! It is NULL:


  CPU 12 Unable to handle kernel paging request at virtual address
0000000000000048, epc == ffffffff80de37ec, ra == ffffffff80c7c
Oops[#1]:
CPU: 12 PID: 1502 Comm: kworker/12:1 Not tainted 4.9.43-Cavium-Octeon+ #1
Workqueue: events_power_efficient phy_state_machine
task: 80000004021ed100 task.stack: 8000000409d70000
$ 0   : 0000000000000000 ffffffff84720060 0000000000000048 0000000000000004
$ 4   : 0000000000000000 0000000000000001 0000000000000004 0000000000000000
$ 8   : 0000000000000000 0000000000000000 00000000ffff98f3 0000000000000000
$12   : 8000000409d73fe0 0000000000009c00 ffffffff846547c8 000000000000af3b
$16   : 80000004096bab68 80000004096babd0 0000000000000000 80000004096ba800
$20   : 0000000000000000 0000000000000000 ffffffff81090000 0000000000000008
$24   : 0000000000000061 ffffffff808637b0
$28   : 8000000409d70000 8000000409d73cf0 80000000271bd300 ffffffff80c7804c
Hi    : 000000000000002a
Lo    : 000000000000003f
epc   : ffffffff80de37ec netif_carrier_off+0xc/0x58
ra    : ffffffff80c7804c phy_state_machine+0x48c/0x4f8
Status: 14009ce3        KX SX UX KERNEL EXL IE
Cause : 00800008 (ExcCode 02)
BadVA : 0000000000000048
PrId  : 000d9501 (Cavium Octeon III)
Modules linked in:
Process kworker/12:1 (pid: 1502, threadinfo=8000000409d70000,
task=80000004021ed100, tls=0000000000000000)
Stack : 8000000409a54000 80000004096bab68 80000000271bd300 80000000271c1e00
         0000000000000000 ffffffff808a1708 8000000409a54000 80000000271bd300
         80000000271bd320 8000000409a54030 ffffffff80ff0f00 0000000000000001
         ffffffff81090000 ffffffff808a1ac0 8000000402182080 ffffffff84650000
         8000000402182080 ffffffff84650000 ffffffff80ff0000 8000000409a54000
         ffffffff808a1970 0000000000000000 80000004099e8000 8000000402099240
         0000000000000000 ffffffff808a8598 0000000000000000 8000000408eeeb00
         8000000409a54000 00000000810a1d00 0000000000000000 8000000409d73de8
         8000000409d73de8 0000000000000088 000000000c009c00 8000000409d73e08
         8000000409d73e08 8000000402182080 ffffffff808a84d0 8000000402182080
         ...
Call Trace:
[<ffffffff80de37ec>] netif_carrier_off+0xc/0x58
[<ffffffff80c7804c>] phy_state_machine+0x48c/0x4f8
[<ffffffff808a1708>] process_one_work+0x158/0x368
[<ffffffff808a1ac0>] worker_thread+0x150/0x4c0
[<ffffffff808a8598>] kthread+0xc8/0xe0
[<ffffffff808617f0>] ret_from_kernel_thread+0x14/0x1c