Re: [PATCH net v4] net: fix race between napi kthread mode and busy poll

[Martin Zaharinov <micron10@gmail.com>]

Hi Eric 
May be I write to Wai to check yet.

And one other problem may be is for network team and I don't know how much it has to do with it.

Mar 20 06:06:28 [367562.703896][T1217504] team0: Failed to send options change via netlink (err -105)
Mar 20 06:06:33 [367567.824137][T1217504] team0: Failed to send options change via netlink (err -105)
Mar 20 06:06:39 [367572.944079][T1217504] team0: Failed to send options change via netlink (err -105)
Mar 20 06:06:44 [367578.064217][T1217504] team0: Failed to send options change via netlink (err -105)
Mar 20 06:06:49 [367583.184378][T1217504] team0: Failed to send options change via netlink (err -105)
Mar 20 06:06:54 [367588.304470][T1217504] team0: Failed to send options change via netlink (err -105)
Mar 20 06:06:59 [367593.414634][T1217504] team0: Failed to send options change via netlink (err -105)
Mar 20 06:07:04 [367598.534996][T1217504] team0: Failed to send options change via netlink (err -105)
Mar 20 06:07:09 [367603.664872][T1217504] team0: Failed to send options change via netlink (err -105)
Mar 20 06:07:14 [367608.785017][T1217504] team0: Failed to send options change via netlink (err -105)
Mar 20 06:07:20 [367613.905101][T1217504] team0: Failed to send options change via netlink (err -105)
Mar 20 06:07:25 [367619.025236][T1217504] team0: Failed to send options change via netlink (err -105)
Mar 20 06:07:30 [367624.145448][T1217504] team0: Failed to send options change via netlink (err -105)
Mar 20 06:07:35 [367629.265489][T1217504] team0: Failed to send options change via netlink (err -105)
Mar 20 06:07:40 [367634.385630][T1217504] team0: Failed to send options change via netlink (err -105)


when this happens it stops connecting to the server


Martin	

> On 20 Mar 2021, at 11:55, Eric Dumazet <edumazet@google.com> wrote:
> 
> On Sat, Mar 20, 2021 at 9:45 AM Martin Zaharinov <micron10@gmail.com> wrote:
>> 
>> Hi Wei
>> Check this:
>> 
>> [   39.706567] ------------[ cut here ]------------
>> [   39.706568] RTNL: assertion failed at net/ipv4/udp_tunnel_nic.c (557)
>> [   39.706585] WARNING: CPU: 0 PID: 429 at net/ipv4/udp_tunnel_nic.c:557 __udp_tunnel_nic_reset_ntf+0xea/0x100
> 
> Probably more relevant to Intel maintainers than Wei :/
> 
>> [   39.706594] Modules linked in: i40e(+) nf_nat_sip nf_conntrack_sip nf_nat_pptp nf_conntrack_pptp nf_nat_tftp nf_conntrack_tftp nf_nat_ftp nf_conntrack_ftp nf_nat nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 acpi_ipmi ipmi_si ipmi_devintf ipmi_msghandler rtc_cmos megaraid_sas
>> [   39.706614] CPU: 0 PID: 429 Comm: kworker/0:2 Tainted: G           O      5.11.7 #1
>> [   39.706618] Hardware name: Supermicro X11DPi-N(T)/X11DPi-NT, BIOS 3.4 11/23/2020
>> [   39.706619] Workqueue: events work_for_cpu_fn
>> [   39.706627] RIP: 0010:__udp_tunnel_nic_reset_ntf+0xea/0x100
>> [   39.706631] Code: c0 79 f1 00 00 0f 85 4e ff ff ff ba 2d 02 00 00 48 c7 c6 45 3c 3a 93 48 c7 c7 40 de 39 93 c6 05 a0 79 f1 00 01 e8 f5 ad 0c 00 <0f> 0b e9 28 ff ff ff 66 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00
>> [   39.706634] RSP: 0018:ffffa8390d9b3b38 EFLAGS: 00010292
>> [   39.706637] RAX: 0000000000000039 RBX: ffff8e02630b2768 RCX: 00000000ffdfffff
>> [   39.706639] RDX: 00000000ffdfffff RSI: ffff8e80ad400000 RDI: 0000000000000001
>> [   39.706641] RBP: ffff8e025df72000 R08: ffff8e80bb3fffe8 R09: 00000000ffffffea
>> [   39.706643] R10: 00000000ffdfffff R11: 80000000ffe00000 R12: ffff8e02630b2008
>> [   39.706645] R13: 0000000000000000 R14: ffff8e024a88ba00 R15: 0000000000000000
>> [   39.706646] FS:  0000000000000000(0000) GS:ffff8e40bf800000(0000) knlGS:0000000000000000
>> [   39.706649] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>> [   39.706651] CR2: 00000000004d8f40 CR3: 0000002ca140a002 CR4: 00000000001706f0
>> [   39.706652] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
>> [   39.706654] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
>> [   39.706656] Call Trace:
>> [   39.706658]  i40e_setup_pf_switch+0x617/0xf80 [i40e]
>> [   39.706683]  i40e_probe.part.0.cold+0x8dc/0x109e [i40e]
>> [   39.706708]  ? acpi_ns_check_object_type+0xd4/0x193
>> [   39.706713]  ? acpi_ns_check_package_list+0xfd/0x205
>> [   39.706716]  ? __kmalloc+0x37/0x160
>> [   39.706720]  ? kmem_cache_alloc+0xcb/0x120
>> [   39.706723]  ? irq_get_irq_data+0x5/0x20
>> [   39.706726]  ? mp_check_pin_attr+0xe/0xf0
>> [   39.706729]  ? irq_get_irq_data+0x5/0x20
>> [   39.706731]  ? mp_map_pin_to_irq+0xb7/0x2c0
>> [   39.706735]  ? acpi_register_gsi_ioapic+0x86/0x150
>> [   39.706739]  ? pci_conf1_read+0x9f/0xf0
>> [   39.706743]  ? pci_bus_read_config_word+0x2e/0x40
>> [   39.706746]  local_pci_probe+0x1b/0x40
>> [   39.706750]  work_for_cpu_fn+0xb/0x20
>> [   39.706754]  process_one_work+0x1ec/0x350
>> [   39.706758]  worker_thread+0x24b/0x4d0
>> [   39.706760]  ? process_one_work+0x350/0x350
>> [   39.706762]  kthread+0xea/0x120
>> [   39.706766]  ? kthread_park+0x80/0x80
>> [   39.706770]  ret_from_fork+0x1f/0x30
>> [   39.706774] ---[ end trace 7a203f3ec972a377 ]---
>> 
>> Martin
>> 
>> 
>>> On 17 Mar 2021, at 0:36, Wei Wang <weiwan@google.com> wrote:
>>> 
>>> Currently, napi_thread_wait() checks for NAPI_STATE_SCHED bit to
>>> determine if the kthread owns this napi and could call napi->poll() on
>>> it. However, if socket busy poll is enabled, it is possible that the
>>> busy poll thread grabs this SCHED bit (after the previous napi->poll()
>>> invokes napi_complete_done() and clears SCHED bit) and tries to poll
>>> on the same napi. napi_disable() could grab the SCHED bit as well.
>>> This patch tries to fix this race by adding a new bit
>>> NAPI_STATE_SCHED_THREADED in napi->state. This bit gets set in
>>> ____napi_schedule() if the threaded mode is enabled, and gets cleared
>>> in napi_complete_done(), and we only poll the napi in kthread if this
>>> bit is set. This helps distinguish the ownership of the napi between
>>> kthread and other scenarios and fixes the race issue.
>>> 
>>> Fixes: 29863d41bb6e ("net: implement threaded-able napi poll loop support")
>>> Reported-by: Martin Zaharinov <micron10@gmail.com>
>>> Suggested-by: Jakub Kicinski <kuba@kernel.org>
>>> Signed-off-by: Wei Wang <weiwan@google.com>
>>> Cc: Alexander Duyck <alexanderduyck@fb.com>
>>> Cc: Eric Dumazet <edumazet@google.com>
>>> Cc: Paolo Abeni <pabeni@redhat.com>
>>> Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
>>> ---
>>> Change since v3:
>>> - Add READ_ONCE() for thread->state and add comments in
>>>   ____napi_schedule().
>>> 
>>> include/linux/netdevice.h |  2 ++
>>> net/core/dev.c            | 19 ++++++++++++++++++-
>>> 2 files changed, 20 insertions(+), 1 deletion(-)
>>> 
>>> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>>> index 5b67ea89d5f2..87a5d186faff 100644
>>> --- a/include/linux/netdevice.h
>>> +++ b/include/linux/netdevice.h
>>> @@ -360,6 +360,7 @@ enum {
>>>      NAPI_STATE_IN_BUSY_POLL,        /* sk_busy_loop() owns this NAPI */
>>>      NAPI_STATE_PREFER_BUSY_POLL,    /* prefer busy-polling over softirq processing*/
>>>      NAPI_STATE_THREADED,            /* The poll is performed inside its own thread*/
>>> +     NAPI_STATE_SCHED_THREADED,      /* Napi is currently scheduled in threaded mode */
>>> };
>>> 
>>> enum {
>>> @@ -372,6 +373,7 @@ enum {
>>>      NAPIF_STATE_IN_BUSY_POLL        = BIT(NAPI_STATE_IN_BUSY_POLL),
>>>      NAPIF_STATE_PREFER_BUSY_POLL    = BIT(NAPI_STATE_PREFER_BUSY_POLL),
>>>      NAPIF_STATE_THREADED            = BIT(NAPI_STATE_THREADED),
>>> +     NAPIF_STATE_SCHED_THREADED      = BIT(NAPI_STATE_SCHED_THREADED),
>>> };
>>> 
>>> enum gro_result {
>>> diff --git a/net/core/dev.c b/net/core/dev.c
>>> index 6c5967e80132..d3195a95f30e 100644
>>> --- a/net/core/dev.c
>>> +++ b/net/core/dev.c
>>> @@ -4294,6 +4294,13 @@ static inline void ____napi_schedule(struct softnet_data *sd,
>>>               */
>>>              thread = READ_ONCE(napi->thread);
>>>              if (thread) {
>>> +                     /* Avoid doing set_bit() if the thread is in
>>> +                      * INTERRUPTIBLE state, cause napi_thread_wait()
>>> +                      * makes sure to proceed with napi polling
>>> +                      * if the thread is explicitly woken from here.
>>> +                      */
>>> +                     if (READ_ONCE(thread->state) != TASK_INTERRUPTIBLE)
>>> +                             set_bit(NAPI_STATE_SCHED_THREADED, &napi->state);
>>>                      wake_up_process(thread);
>>>                      return;
>>>              }
>>> @@ -6486,6 +6493,7 @@ bool napi_complete_done(struct napi_struct *n, int work_done)
>>>              WARN_ON_ONCE(!(val & NAPIF_STATE_SCHED));
>>> 
>>>              new = val & ~(NAPIF_STATE_MISSED | NAPIF_STATE_SCHED |
>>> +                           NAPIF_STATE_SCHED_THREADED |
>>>                            NAPIF_STATE_PREFER_BUSY_POLL);
>>> 
>>>              /* If STATE_MISSED was set, leave STATE_SCHED set,
>>> @@ -6968,16 +6976,25 @@ static int napi_poll(struct napi_struct *n, struct list_head *repoll)
>>> 
>>> static int napi_thread_wait(struct napi_struct *napi)
>>> {
>>> +     bool woken = false;
>>> +
>>>      set_current_state(TASK_INTERRUPTIBLE);
>>> 
>>>      while (!kthread_should_stop() && !napi_disable_pending(napi)) {
>>> -             if (test_bit(NAPI_STATE_SCHED, &napi->state)) {
>>> +             /* Testing SCHED_THREADED bit here to make sure the current
>>> +              * kthread owns this napi and could poll on this napi.
>>> +              * Testing SCHED bit is not enough because SCHED bit might be
>>> +              * set by some other busy poll thread or by napi_disable().
>>> +              */
>>> +             if (test_bit(NAPI_STATE_SCHED_THREADED, &napi->state) || woken) {
>>>                      WARN_ON(!list_empty(&napi->poll_list));
>>>                      __set_current_state(TASK_RUNNING);
>>>                      return 0;
>>>              }
>>> 
>>>              schedule();
>>> +             /* woken being true indicates this thread owns this napi. */
>>> +             woken = true;
>>>              set_current_state(TASK_INTERRUPTIBLE);
>>>      }
>>>      __set_current_state(TASK_RUNNING);
>>> --
>>> 2.31.0.rc2.261.g7f71774620-goog
>>> 
>>