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.
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).
>
