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Re: Linux 5.0 regression: rtl8169 / kernel BUG at lib/dynamic_queue_limits.c:27!




On 10.02.2019 14:05, Sander Eikelenboom wrote:
> On 10/02/2019 12:44, Heiner Kallweit wrote:
>> On 10.02.2019 10:16, Sander Eikelenboom wrote:
>>> On 09/02/2019 12:50, Heiner Kallweit wrote:
>>>> On 09.02.2019 11:07, Sander Eikelenboom wrote:
>>>>> On 09/02/2019 10:59, Heiner Kallweit wrote:
>>>>>> On 09.02.2019 10:34, Sander Eikelenboom wrote:
>>>>>>> On 09/02/2019 10:02, Heiner Kallweit wrote:
>>>>>>>> On 09.02.2019 00:09, Eric Dumazet wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On 02/08/2019 01:50 PM, Heiner Kallweit wrote:
>>>>>>>>>> On 08.02.2019 22:45, Sander Eikelenboom wrote:
>>>>>>>>>>> On 08/02/2019 22:22, Heiner Kallweit wrote:
>>>>>>>>>>>> On 08.02.2019 21:55, Sander Eikelenboom wrote:
>>>>>>>>>>>>> On 08/02/2019 19:52, Heiner Kallweit wrote:
>>>>>>>>>>>>>> On 08.02.2019 19:29, Sander Eikelenboom wrote:
>>>>>>>>>>>>>>> L.S.,
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> While testing a linux 5.0-rc5 kernel (with some patches on top but they don't seem related) under Xen i the nasty splat below, 
>>>>>>>>>>>>>>> that I haven encountered with Linux 4.20.x.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> Unfortunately I haven't got a clear reproducer for this and bisecting could be nasty due to another (networking related) kernel bug.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> If you need more info, want me to run a debug patch etc., please feel free to ask.
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>> Thanks for the report. However I see no change in the r8169 driver between
>>>>>>>>>>>>>> 4.20 and 5.0 with regard to BQL code. Having said that the root cause could
>>>>>>>>>>>>>> be somewhere else. Therefore I'm afraid a bisect will be needed.
>>>>>>>>>>>>>
>>>>>>>>>>>>> Hmm i did some diging and i think:
>>>>>>>>>>>>> bd7153bd83b806bfcc2e79b7a6f43aa653d06ef3 r8169: remove unneeded mmiowb barriers
>>>>>>>>>>>>> 2e6eedb4813e34d8d84ac0eb3afb668966f3f356 r8169: make use of xmit_more and __netdev_sent_queue
>>>>>>>>>>>>> 620344c43edfa020bbadfd81a144ebe5181fc94f net: core: add __netdev_sent_queue as variant of __netdev_tx_sent_queue
>>>>>>>>>>>>>
>>>>>>>>>>>> You're right. Thought this was added in 4.20 already.
>>>>>>>>>>>> The BQL code pattern I copied from the mlx4 driver and so far I haven't heard about
>>>>>>>>>>>> this issue from any user of physical hw. And due to the fact that a lot of mainboards
>>>>>>>>>>>> have onboard Realtek network I have quite a few testers out there.
>>>>>>>>>>>> Does the issue occur under specific circumstances like very high load?
>>>>>>>>>>>
>>>>>>>>>>> Yep, the box is already quite contented with the Xen VM's and if I remember correctly it occurred while kernel compiling
>>>>>>>>>>> on the host.
>>>>>>>>>>>
>>>>>>>>>>>> If indeed the xmit_more patch causes the issue, I think we have to involve Eric Dumazet
>>>>>>>>>>>> as author of the underlying changes.
>>>>>>>>>>>
>>>>>>>>>>> It could also be the barriers weren't that unneeded as assumed.
>>>>>>>>>>
>>>>>>>>>> The barriers were removed after adding xmit_more handling. Therefore it would be good to
>>>>>>>>>> test also with only 
>>>>>>>>>> bd7153bd83b806bfcc2e79b7a6f43aa653d06ef3 r8169: remove unneeded mmiowb barriers
>>>>>>>>>> removed.
>>>>>>>>>>
>>>>>>>>>>> Since we are almost at RC6 i took the liberty to CC Eric now.
>>>>>>>>>>>
>>>>>>>>>> Sure, thanks.
>>>>>>>>>>
>>>>>>>>>>> BTW am i correct these patches are merely optimizations ?
>>>>>>>>>>
>>>>>>>>>> Yes
>>>>>>>>>>
>>>>>>>>>>> If so and concluding they revert cleanly, perhaps it should be considered at this point in the RC's
>>>>>>>>>>> to revert them for 5.0 and try again for 5.1 ?
>>>>>>>>>>>
>>>>>>>>>> Before removing both it would be good to test with only the barrier-removal removed.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>> Commit 2e6eedb4813e34d8d84ac0eb3afb668966f3f356 r8169: make use of xmit_more and __netdev_sent_queue
>>>>>>>>> looks buggy to me, since the skb might have been freed already on another cpu when you call
>>>>>>>>>
>>>>>>>>> You could try :
>>>>>>>>>
>>>>>>>>> diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
>>>>>>>>> index 3624e67aef72c92ed6e908e2c99ac2d381210126..f907d484165d9fd775e81bf2bfb9aa4ddedb1c93 100644
>>>>>>>>> --- a/drivers/net/ethernet/realtek/r8169.c
>>>>>>>>> +++ b/drivers/net/ethernet/realtek/r8169.c
>>>>>>>>> @@ -6070,6 +6070,7 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
>>>>>>>>>         dma_addr_t mapping;
>>>>>>>>>         u32 opts[2], len;
>>>>>>>>>         bool stop_queue;
>>>>>>>>> +       bool door_bell;
>>>>>>>>>         int frags;
>>>>>>>>>  
>>>>>>>>>         if (unlikely(!rtl_tx_slots_avail(tp, skb_shinfo(skb)->nr_frags))) {
>>>>>>>>> @@ -6116,6 +6117,8 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
>>>>>>>>>         /* Force memory writes to complete before releasing descriptor */
>>>>>>>>>         dma_wmb();
>>>>>>>>>  
>>>>>>>>> +       door_bell = __netdev_sent_queue(dev, skb->len, skb->xmit_more);
>>>>>>>>> +
>>>>>>>>>         txd->opts1 = rtl8169_get_txd_opts1(opts[0], len, entry);
>>>>>>>>>  
>>>>>>>>>         /* Force all memory writes to complete before notifying device */
>>>>>>>>> @@ -6127,7 +6130,7 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
>>>>>>>>>         if (unlikely(stop_queue))
>>>>>>>>>                 netif_stop_queue(dev);
>>>>>>>>>  
>>>>>>>>> -       if (__netdev_sent_queue(dev, skb->len, skb->xmit_more)) {
>>>>>>>>> +       if (door_bell) {
>>>>>>>>>                 RTL_W8(tp, TxPoll, NPQ);
>>>>>>>>>                 mmiowb();
>>>>>>>>>         }
>>>>>>>>>
>>>>>>>> Thanks a lot for checking and for the proposed fix.
>>>>>>>> Sander, can you try with this patch on top of 5.0-rc5 w/o removing two two commits?
>>>>>>>
>>>>>>> I have done that already during the night .. the results:
>>>>>>> - I can confirm 2e6eedb4813e34d8d84ac0eb3afb668966f3f356 is the first commit which causes hitting the BUG_ON in lib/dynamic_queue_limits.c.
>>>>>>>   (in other word, with only reverting bd7153bd83b806bfcc2e79b7a6f43aa653d06ef3 it still blows up).
>>>>>>>
>>>>>>> - The Eric's patch only applies cleanly with bd7153bd83b806bfcc2e79b7a6f43aa653d06ef3 reverted, so that's what I tested.
>>>>>>>   The patch seems to prevent hitting the BUG_ON in lib/dynamic_queue_limits.c, it has run this night and I gave done a few kernel compiles
>>>>>>>   this morning. How ever during these kernel compiles i'm getting a transmit queue timeout which i haven't seen with 4.20.x, although i regularly
>>>>>>>   compile kernels in the same way as I do now. The only thing I can't say if that is due to this change, or if it's again something else.
>>>>>>>   Which makes me somewhat inclined to go testing the complete revert some more and see if I can trigger the queue timeout on that or not.
>>>>>>>
>>>>>>>   If I can, it is a separate issue.
>>>>>>>   If I can't it seems even with a patch it still seems as a regression in comparison with 4.20.x, for which
>>>>>>>   a revert would be the right thing to do (since as you indicated these are merely optimizations), 
>>>>>>>   which would give us more time for 5.1 to try to solve things on top of the 5.0-release-to-be.
>>>>>>>   (especially since I seem to still have other issues which need to be sorted out and time is limited)
>>>>>>>
>>>>>>>   The timeout in question:
>>>>>>>         [28336.869479] NETDEV WATCHDOG: eth1 (r8169): transmit queue 0 timed out
>>>>>>>         [28336.881498] WARNING: CPU: 0 PID: 6925 at net/sched/sch_generic.c:461 dev_watchdog+0x20b/0x210
>>>>>>>         [28336.893358] Modules linked in:
>>>>>>>         [28336.904106] CPU: 0 PID: 6925 Comm: cc1 Tainted: G      D           5.0.0-rc5-20190208-thp-net-florian-rtl8169-eric-doflr+ #1
>>>>>>>         [28336.917385] Hardware name: MSI MS-7640/890FXA-GD70 (MS-7640)  , BIOS V1.8B1 09/13/2010
>>>>>>>         [28336.928988] RIP: e030:dev_watchdog+0x20b/0x210
>>>>>>>         [28336.940623] Code: 00 49 63 4e e0 eb 90 4c 89 e7 c6 05 ad d8 f1 00 01 e8 a9 32 fd ff 89 d9 48 89 c2 4c 89 e6 48 c7 c7 50 59 89 82 e8 e5 92 4d ff <0f> 0b eb c0 90 48 c7 47 08 00 00 00 00 48 c7 07 00 00 00 00 0f b7
>>>>>>>         [28336.965265] RSP: e02b:ffff88807d403ea0 EFLAGS: 00010286
>>>>>>>         [28336.977465] RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff82a69db8
>>>>>>>         [28336.991265] RDX: 0000000000000001 RSI: 0000000000000001 RDI: 0000000000000200
>>>>>>>         [28337.008865] RBP: ffff88807936e41c R08: 0000000000000000 R09: 0000000000000819
>>>>>>>         [28337.022250] R10: 0000000000000202 R11: ffffffff8247ca80 R12: ffff88807936e000
>>>>>>>         [28337.035204] R13: 0000000000000000 R14: ffff88807936e440 R15: 0000000000000001
>>>>>>>         [28337.049832] FS:  00007f53e9bf3840(0000) GS:ffff88807d400000(0000) knlGS:0000000000000000
>>>>>>>         [28337.062524] CS:  e030 DS: 0000 ES: 0000 CR0: 0000000080050033
>>>>>>>         [28337.075086] CR2: 00007f53e60c4000 CR3: 000000001a0be000 CR4: 0000000000000660
>>>>>>>         [28337.090052] Call Trace:
>>>>>>>         [28337.103615]  <IRQ>
>>>>>>>         [28337.116587]  ? qdisc_destroy+0x120/0x120
>>>>>>>         [28337.128905]  call_timer_fn+0x19/0x90
>>>>>>>         [28337.141892]  expire_timers+0x8b/0xa0
>>>>>>>         [28337.153354]  run_timer_softirq+0x7e/0x160
>>>>>>>         [28337.165931]  ? handle_irq_event_percpu+0x4c/0x70
>>>>>>>         [28337.176548]  ? handle_percpu_irq+0x32/0x50
>>>>>>>         [28337.186734]  __do_softirq+0xed/0x229
>>>>>>>         [28337.196404]  ? hypervisor_callback+0xa/0x20
>>>>>>>         [28337.207822]  irq_exit+0xb7/0xc0
>>>>>>>         [28337.218978]  xen_evtchn_do_upcall+0x27/0x40
>>>>>>>         [28337.230763]  xen_do_hypervisor_callback+0x29/0x40
>>>>>>>         [28337.241261]  </IRQ>
>>>>>>>         [28337.253283] RIP: e033:0xff7e62
>>>>>>>         [28337.264899] Code: 35 43 0f c7 00 4c 89 ef e8 8b 6d 67 ff 0f 1f 00 44 89 e0 44 89 e2 c1 e8 06 83 e2 3f 48 8b 0c c5 40 8d c6 01 48 0f a3 d1 72 0e <48> 8b 04 c5 50 8d c6 01 48 0f a3 d0 73 0b 44 89 e6 4c 89 ef e8 b5
>>>>>>>         [28337.288677] RSP: e02b:00007fff0fc6a340 EFLAGS: 00000202
>>>>>>>         [28337.299234] RAX: 0000000000000000 RBX: 00007f53e60c3580 RCX: 0000000000000000
>>>>>>>         [28337.309577] RDX: 0000000000000034 RSI: 0000000001e71a98 RDI: 00007fff0fc6a538
>>>>>>>         [28337.320724] RBP: 00007fff0fc6a4b0 R08: 0000000000000000 R09: 0000000000000000
>>>>>>>         [28337.331829] R10: 0000000000000001 R11: 00000000020cb3d0 R12: 0000000000000034
>>>>>>>         [28337.343900] R13: 00007fff0fc6a538 R14: 0000000000000000 R15: 0000000000000001
>>>>>>>         [28337.353977] ---[ end trace 6ff49f09286816b7 ]---
>>>>>>>
>>>>>> Thanks for your efforts. As usual this tx timeout trace says basically nothing except
>>>>>> "timeout" and root cause could be anything. Earlier you reported a memory allocation error,
>>>>>> did that occur again?
>>>>>> If we decide to revert, I'd leave removal of the memory barriers in (as it doesn't seem to
>>>>>> contribute to the issue) and just submit a patch to effectively revert
>>>>>> 2e6eedb4813e34d8d84ac0eb3afb668966f3f356.
>>>>>
>>>>> I can't say if that is correct, because i haven't tested that.
>>>>>
>>>>> Another thing I could test is:
>>>>>  - putting all the r8169 patches (and prerequisites) that went into 5.0 
>>>>>    up to bd7153bd83b806bfcc2e79b7a6f43aa653d06ef3, onto 4.20.7 and see what that does.
>>>>>    If that would be feasible (not too many needed prerequisites out of r8169) and if 
>>>>>    you could spare me some time and prep such a branch somewhere so i can pull and compile that,
>>>>>    that would be great.
>>>>>
>>>>
>>>> Unfortunately there's quite a number of changes. Regarding __netdev_tx_sent_queue()
>>>> and watchdog timeout I found the following comment in drivers/net/ethernet/sfc/tx.c,
>>>> efx_enqueue_skb():
>>>>
>>>> 	if (__netdev_tx_sent_queue(tx_queue->core_txq, skb_len, xmit_more)) {
>>>> 		struct efx_tx_queue *txq2 = efx_tx_queue_partner(tx_queue);
>>>>
>>>> 		/* There could be packets left on the partner queue if those
>>>> 		 * SKBs had skb->xmit_more set. If we do not push those they
>>>> 		 * could be left for a long time and cause a netdev watchdog.
>>>> 		 */
>>>> 		if (txq2->xmit_more_available)
>>>> 			efx_nic_push_buffers(txq2);
>>>>
>>>> But I'm not sure whether the situation in r8169 is comparable. The following patch
>>>> implements what I mentioned earlier: It leaves all other 5.0 changes in place and
>>>> effectively reverts 2e6eedb4813e34d8d84ac0eb3afb668966f3f356. Would be great if
>>>> you could give it a try.
>>>
>>> Hi Heiner,
>>>
>>> It took some time to respond, because I had another issue with 5.0 which intervened with proper testing, 
>>> but fortunately I could pinpoint without doing a full bisect and revert that commit for further testing.
>>>
>>> So there is still time left and I could do a more proper run with your patch below.
>>> Unfortunately i still get a splat (see below) with this, although i'm not sure it is related, 
>>> just that I can't tell.
>>>
>> I checked further and there's a handful of network drivers using __napi_alloc_skb() with __GFP_NOWARN,
>> maybe to avoid such splats. Did the splat impact functionality? When checking the code in r8169 the
>> affected packet would just be dropped.
> 
> It doesn't permanently or noticeably impact functionality, and indeed seems to drop packets:
> 
> eth1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
>         inet 172.16.1.1  netmask 255.255.0.0  broadcast 172.16.255.255
>         ether 40:61:86:f4:67:d8  txqueuelen 1000  (Ethernet)
>         RX packets 11563913  bytes 16724445852 (15.5 GiB)
>         RX errors 0  dropped 6  overruns 0  frame 0
>         TX packets 4301515  bytes 1210966808 (1.1 GiB)
>         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
> 
> Reverting 5317d5c6d47e ("r8169: use napi_consume_skb where possible") doesn't suffice still gives the page allocation failure.
> 
> I think at this point in time we should at least get the
> reverts into 5.0 (probably to late for rc-6 since DaveM's pull request is already in) for:
>     bd7153bd83b806bfcc2e79b7a6f43aa653d06ef3 r8169: remove unneeded mmiowb barriers
>     2e6eedb4813e34d8d84ac0eb3afb668966f3f356 r8169: make use of xmit_more and __netdev_sent_queue
> 
OK, I just sent the reverts for both patches.

Heiner

> Commit 2e6eedb4813e34d8d84ac0eb3afb668966f3f356 is the one which caused the BUG_ON() to be hit.
> 
> While we could use your patch to revert only 2e6eedb4813e34d8d84ac0eb3afb668966f3f356 and leave
> bd7153bd83b806bfcc2e79b7a6f43aa653d06ef3 in:
>     - I haven't been able to test it properly.
>     - It's dealing with barriers, which can be tedious and give subtle breakage.
>     - I don't see any compelling argument to keep it in (it's no fix).
>     - It's RC-6 time ...
> 
> So we then we can focus on the page allocation issue and hopefully find some stable
> baseline before 5.0-final is cut. While I appreciate having a forward looking approach,
> I think we are at the point in time, were we should revert when in doubt 
> (and it doesn't clearly fix an other issue).
> 
> After establishing a stable baseline again, we can start incrementally re-applying and test stuff.
> 
> --
> Sander
> 
> 
> 
>>> Perhaps Linus as Oops-decoding-guru has an idea ?
>>>
>>> --
>>> Sander
>>>
>>> [39041.689007] dpkg-deb: page allocation failure: order:0, mode:0x480020(GFP_ATOMIC), nodemask=(null),cpuset=/,mems_allowed=0
>>> [39041.689016] CPU: 4 PID: 14078 Comm: dpkg-deb Not tainted 5.0.0-rc5-20190209-kallweit+ #1
>>> [39041.689017] Hardware name: MSI MS-7640/890FXA-GD70 (MS-7640)  , BIOS V1.8B1 09/13/2010
>>> [39041.689018] Call Trace:
>>> [39041.689022]  <IRQ>
>>> [39041.689030]  dump_stack+0x5c/0x7b
>>> [39041.689033]  warn_alloc+0x103/0x190
>>> [39041.689036]  __alloc_pages_nodemask+0xe3d/0xe80
>>> [39041.689039]  ? ip_rcv+0x48/0xc0
>>> [39041.689040]  ? ip_rcv_finish_core.isra.0+0x360/0x360
>>> [39041.689042]  page_frag_alloc+0x117/0x150
>>> [39041.689044]  __napi_alloc_skb+0x83/0xd0
>>> [39041.689048]  rtl8169_poll+0x210/0x640
>>> [39041.689051]  net_rx_action+0x23d/0x370
>>> [39041.689054]  __do_softirq+0xed/0x229
>>> [39041.689058]  irq_exit+0xb7/0xc0
>>> [39041.689061]  xen_evtchn_do_upcall+0x27/0x40
>>> [39041.689063]  xen_do_hypervisor_callback+0x29/0x40
>>> [39041.689064]  </IRQ>
>>> [39041.689066] RIP: e030:_atomic_dec_and_lock+0x2/0x40
>>> [39041.689068] Code: ff 39 05 c5 c1 c9 00 89 c7 89 c6 76 0f 83 eb 01 83 fb ff 75 d9 5b 89 f8 5d 41 5c c3 0f 0b 90 90 90 90 90 90 90 90 90 90 8b 07 <83> f8 01 74 0c 8d 50 ff f0 0f b1 17 75 f2 31 c0 c3 55 53 48 89 fb
>>> [39041.689069] RSP: e02b:ffffc9000705b990 EFLAGS: 00000246
>>> [39041.689071] RAX: 0000000000000001 RBX: ffff888017082640 RCX: 0000000000000000
>>> [39041.689071] RDX: 0000000000000000 RSI: ffff8880170826c0 RDI: ffff888017082788
>>> [39041.689072] RBP: ffff8880170826c0 R08: ffffc9000705bb00 R09: ffffc9000705bb00
>>> [39041.689073] R10: ffffc9000705bb58 R11: ffff88807fc17000 R12: ffff888017082788
>>> [39041.689073] R13: ffff88806cc8cf58 R14: ffff888017082640 R15: ffff888009990240
>>> [39041.689077]  iput+0x63/0x1a0
>>> [39041.689079]  __dentry_kill+0xc5/0x170
>>> [39041.689080]  shrink_dentry_list+0x93/0x1c0
>>> [39041.689082]  prune_dcache_sb+0x4d/0x70
>>> [39041.689084]  super_cache_scan+0x104/0x190
>>> [39041.689087]  do_shrink_slab+0x12c/0x1e0
>>> [39041.689089]  shrink_slab+0xdf/0x2b0
>>> [39041.689091]  shrink_node+0x158/0x470
>>> [39041.689093]  do_try_to_free_pages+0xd1/0x380
>>> [39041.689095]  try_to_free_pages+0xb2/0xe0
>>> [39041.689097]  __alloc_pages_nodemask+0x603/0xe80
>>> [39041.689099]  ? __pagevec_lru_add_fn+0x1b1/0x290
>>> [39041.689102]  alloc_pages_vma+0x7b/0x1c0
>>> [39041.689106]  __handle_mm_fault+0xdb3/0x1060
>>> [39041.689109]  ? xen_mc_flush+0xc0/0x190
>>> [39041.689110]  handle_mm_fault+0xf8/0x200
>>> [39041.689113]  __do_page_fault+0x231/0x4a0
>>> [39041.689115]  ? page_fault+0x8/0x30
>>> [39041.689116]  page_fault+0x1e/0x30
>>> [39041.689118] RIP: e033:0x7fb9851d012e
>>> [39041.689119] Code: 29 c2 48 3b 15 7b a3 31 00 0f 87 af 00 00 00 0f 10 01 0f 10 49 f0 0f 10 51 e0 0f 10 59 d0 48 83 e9 40 48 83 ea 40 41 0f 29 01 <41> 0f 29 49 f0 41 0f 29 51 e0 41 0f 29 59 d0 49 83 e9 40 48 83 fa
>>> [39041.689119] RSP: e02b:00007fb958b36d38 EFLAGS: 00010202
>>> [39041.689120] RAX: 00007fb97a617f0e RBX: 000000000000f004 RCX: 00007fb948008be3
>>> [39041.689121] RDX: 00000000000080c2 RSI: 00007fb948000b31 RDI: 00007fb97a617f0e
>>> [39041.689122] RBP: 00000000000ff062 R08: 0000000000000002 R09: 00007fb97a620000
>>> [39041.689123] R10: 0000000000000004 R11: 00007fb97a626f02 R12: 000000000000f005
>>> [39041.689123] R13: 00007fb948000b28 R14: 0000562d76b63710 R15: 0000000000000003
>>> [39041.689125] Mem-Info:
>>> [39041.689130] active_anon:78775 inactive_anon:49211 isolated_anon:0
>>>                 active_file:106409 inactive_file:107531 isolated_file:0
>>>                 unevictable:552 dirty:175 writeback:0 unstable:0
>>>                 slab_reclaimable:13739 slab_unreclaimable:16454
>>>                 mapped:1605 shmem:23 pagetables:2900 bounce:0
>>>                 free:3681 free_pcp:935 free_cma:0
>>> [39041.689132] Node 0 active_anon:315100kB inactive_anon:196844kB active_file:425636kB inactive_file:430124kB unevictable:2208kB isolated(anon):0kB isolated(file):0kB mapped:6420kB dirty:700kB writeback:0kB shmem:92kB shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 0kB writeback_tmp:0kB unstable:0kB all_unreclaimable? no
>>> [39041.689133] Node 0 DMA free:7480kB min:44kB low:56kB high:68kB active_anon:0kB inactive_anon:7832kB active_file:472kB inactive_file:4kB unevictable:0kB writepending:0kB present:15956kB managed:15872kB mlocked:0kB kernel_stack:0kB pagetables:12kB bounce:0kB free_pcp:0kB local_pcp:0kB free_cma:0kB
>>> [39041.689136] lowmem_reserve[]: 0 1865 1865 1865
>>> [39041.689138] Node 0 DMA32 free:7244kB min:19472kB low:21380kB high:23288kB active_anon:315360kB inactive_anon:188144kB active_file:425164kB inactive_file:430120kB unevictable:2208kB writepending:700kB present:2080768kB managed:1674968kB mlocked:2208kB kernel_stack:9632kB pagetables:11588kB bounce:0kB free_pcp:3740kB local_pcp:528kB free_cma:0kB
>>> [39041.689140] lowmem_reserve[]: 0 0 0 0
>>> [39041.689142] Node 0 DMA: 6*4kB (UME) 6*8kB (UE) 7*16kB (UME) 6*32kB (ME) 5*64kB (UME) 3*128kB (UE) 5*256kB (UME) 2*512kB (ME) 2*1024kB (UE) 1*2048kB (M) 0*4096kB = 7480kB
>>> [39041.689148] Node 0 DMA32: 69*4kB (U) 315*8kB (UE) 138*16kB (UE) 70*32kB (UE) 0*64kB 0*128kB 0*256kB 0*512kB 0*1024kB 0*2048kB 0*4096kB = 7244kB
>>> [39041.689153] 214701 total pagecache pages
>>> [39041.689155] 273 pages in swap cache
>>> [39041.689156] Swap cache stats: add 100978, delete 100706, find 1158/1257
>>> [39041.689156] Free swap  = 3790588kB
>>> [39041.689157] Total swap = 4194300kB
>>> [39041.689157] 524181 pages RAM
>>> [39041.689158] 0 pages HighMem/MovableOnly
>>> [39041.689158] 101471 pages reserved
>>> [39041.689159] 0 pages cma reserved
>>>
>>>
>>>
>>>
>>>
>>>> diff --git a/drivers/net/ethernet/realtek/r8169.c b/drivers/net/ethernet/realtek/r8169.c
>>>> index e8a112149..3cca2ffb2 100644
>>>> --- a/drivers/net/ethernet/realtek/r8169.c
>>>> +++ b/drivers/net/ethernet/realtek/r8169.c
>>>> @@ -6192,7 +6192,6 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
>>>>  	struct device *d = tp_to_dev(tp);
>>>>  	dma_addr_t mapping;
>>>>  	u32 opts[2], len;
>>>> -	bool stop_queue;
>>>>  	int frags;
>>>>  
>>>>  	if (unlikely(!rtl_tx_slots_avail(tp, skb_shinfo(skb)->nr_frags))) {
>>>> @@ -6234,6 +6233,8 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
>>>>  
>>>>  	txd->opts2 = cpu_to_le32(opts[1]);
>>>>  
>>>> +	netdev_sent_queue(dev, skb->len);
>>>> +
>>>>  	skb_tx_timestamp(skb);
>>>>  
>>>>  	/* Force memory writes to complete before releasing descriptor */
>>>> @@ -6246,14 +6247,14 @@ static netdev_tx_t rtl8169_start_xmit(struct sk_buff *skb,
>>>>  
>>>>  	tp->cur_tx += frags + 1;
>>>>  
>>>> -	stop_queue = !rtl_tx_slots_avail(tp, MAX_SKB_FRAGS);
>>>> -	if (unlikely(stop_queue))
>>>> -		netif_stop_queue(dev);
>>>> -
>>>> -	if (__netdev_sent_queue(dev, skb->len, skb->xmit_more))
>>>> -		RTL_W8(tp, TxPoll, NPQ);
>>>> +	RTL_W8(tp, TxPoll, NPQ);
>>>>  
>>>> -	if (unlikely(stop_queue)) {
>>>> +	if (!rtl_tx_slots_avail(tp, MAX_SKB_FRAGS)) {
>>>> +		/* Avoid wrongly optimistic queue wake-up: rtl_tx thread must
>>>> +		 * not miss a ring update when it notices a stopped queue.
>>>> +		 */
>>>> +		smp_wmb();
>>>> +		netif_stop_queue(dev);
>>>>  		/* Sync with rtl_tx:
>>>>  		 * - publish queue status and cur_tx ring index (write barrier)
>>>>  		 * - refresh dirty_tx ring index (read barrier).
>>>>
>>>
>>>
>>
> 
>