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Date:   Tue, 6 Apr 2021 11:48:02 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     Oleksandr Natalenko <oleksandr@natalenko.name>
Cc:     linux-kernel@vger.kernel.org,
        Jesse Brandeburg <jesse.brandeburg@intel.com>,
        Tony Nguyen <anthony.l.nguyen@intel.com>,
        "David S. Miller" <davem@davemloft.net>,
        intel-wired-lan@lists.osuosl.org, netdev@vger.kernel.org,
        Alexander Duyck <alexander.duyck@gmail.com>
Subject: Re: [igb] netconsole triggers warning in netpoll_poll_dev
Message-ID: <20210406114734.0e00cb2f@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
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On Tue, 6 Apr 2021 14:36:19 +0200 Oleksandr Natalenko wrote:
> Hello.
> 
> I've raised this here [1] first, but was suggested to engage igb devs,
> so here we are.
> 
> I'm experiencing the following woes while using netconsole regularly:
> 
> ```
> [22038.710800] ------------[ cut here ]------------
> [22038.710801] igb_poll+0x0/0x1440 [igb] exceeded budget in poll
> [22038.710802] WARNING: CPU: 12 PID: 40362 at net/core/netpoll.c:155 netpoll_poll_dev+0x18a/0x1a0
> [22038.710802] Modules linked in: ...
> [22038.710835] CPU: 12 PID: 40362 Comm: systemd-sleep Not tainted 5.11.0-pf7 #1
> [22038.710836] Hardware name: ASUS System Product Name/Pro WS X570-ACE, BIOS 3302 03/05/2021
> [22038.710836] RIP: 0010:netpoll_poll_dev+0x18a/0x1a0
> [22038.710837] Code: 6e ff 80 3d d2 9d f8 00 00 0f 85 5c ff ff ff 48 8b 73 28 48 c7 c7 0c b8 21 84 89 44 24 04 c6 05 b6 9d f8 00 01 e8 84 21 1c 00 <0f> 0b 8b 54 24 04 e9 36 ff ff ff 66 66 2e 0f 1f 84 00 00 00 00 00
> [22038.710838] RSP: 0018:ffffb24106e37ba0 EFLAGS: 00010086
> [22038.710838] RAX: 0000000000000000 RBX: ffff9599d2929c50 RCX: ffff959f8ed1ac30
> [22038.710839] RDX: 0000000000000000 RSI: 0000000000000023 RDI: ffff959f8ed1ac28
> [22038.710839] RBP: ffff9598981d4058 R08: 0000000000000019 R09: ffffb24206e3796d
> [22038.710839] R10: ffffffffffffffff R11: ffffb24106e37968 R12: ffff959887e51ec8
> [22038.710840] R13: 000000000000000c R14: 00000000ffffffff R15: ffff9599d2929c60
> [22038.710840] FS:  00007f3ade370a40(0000) GS:ffff959f8ed00000(0000) knlGS:0000000000000000
> [22038.710841] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [22038.710841] CR2: 0000000000000000 CR3: 00000003017b0000 CR4: 0000000000350ee0
> [22038.710841] Call Trace:
> [22038.710842]  netpoll_send_skb+0x185/0x240
> [22038.710842]  write_msg+0xe5/0x100 [netconsole]
> [22038.710842]  console_unlock+0x37d/0x640
> [22038.710842]  ? __schedule+0x2e5/0xc90
> [22038.710843]  suspend_devices_and_enter+0x2ac/0x7f0
> [22038.710843]  pm_suspend.cold+0x321/0x36c
> [22038.710843]  state_store+0xa6/0x140
> [22038.710844]  kernfs_fop_write_iter+0x124/0x1b0
> [22038.710844]  new_sync_write+0x16a/0x200
> [22038.710844]  vfs_write+0x21c/0x2e0
> [22038.710844]  __x64_sys_write+0x6d/0xf0
> [22038.710845]  do_syscall_64+0x33/0x40
> [22038.710845]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> [22038.710845] RIP: 0033:0x7f3adece10f7
> [22038.710846] Code: 0d 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24
> [22038.710847] RSP: 002b:00007ffc51c555b8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
> [22038.710847] RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 00007f3adece10f7
> [22038.710848] RDX: 0000000000000004 RSI: 00007ffc51c556a0 RDI: 0000000000000004
> [22038.710848] RBP: 00007ffc51c556a0 R08: 000055ea374302a0 R09: 00007f3aded770c0
> [22038.710849] R10: 00007f3aded76fc0 R11: 0000000000000246 R12: 0000000000000004
> [22038.710849] R13: 000055ea3742c430 R14: 0000000000000004 R15: 00007f3adedb3700
> [22038.710849] ---[ end trace 6eae54fbf23807f8 ]---
> ```
> 
> This one happened during suspend/resume cycle (on resume), followed by:
> 
> ```
> [22038.868669] igb 0000:05:00.0 enp5s0: Reset adapter
> [22040.998673] igb 0000:05:00.0 enp5s0: Reset adapter
> [22043.819198] igb 0000:05:00.0 enp5s0: igb: enp5s0 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX
> ```
> 
> I've bumped into a similar issue in BZ 211911 [2] (see c#16),
> and in c#17 it was suggested it was a separate unrelated issue,
> hence I'm raising a new concern.
> 
> Please help in finding out why this woe happens and in fixing it.
> 
> Thanks.
> 
> [1] https://bugzilla.kernel.org/show_bug.cgi?id=212573
> [2] https://bugzilla.kernel.org/show_bug.cgi?id=211911

Looks like igb_clean_tx_irq() should not return true if budget is 0,
ever, otherwise we risk hitting the min(work, budget - 1) which may
go negative.

So something like this? 

diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
index c9e8c65a3cfe..7a237b5311ca 100644
--- a/drivers/net/ethernet/intel/igb/igb_main.c
+++ b/drivers/net/ethernet/intel/igb/igb_main.c
@@ -8028,7 +8028,7 @@ static bool igb_clean_tx_irq(struct igb_q_vector *q_vector, int napi_budget)
        unsigned int i = tx_ring->next_to_clean;
 
        if (test_bit(__IGB_DOWN, &adapter->state))
-               return true;
+               goto out;
 
        tx_buffer = &tx_ring->tx_buffer_info[i];
        tx_desc = IGB_TX_DESC(tx_ring, i);
@@ -8157,7 +8157,7 @@ static bool igb_clean_tx_irq(struct igb_q_vector *q_vector, int napi_budget)
                                            tx_ring->queue_index);
 
                        /* we are about to reset, no point in enabling stuff */
-                       return true;
+                       goto out;
                }
        }
 
@@ -8180,7 +8180,7 @@ static bool igb_clean_tx_irq(struct igb_q_vector *q_vector, int napi_budget)
                        u64_stats_update_end(&tx_ring->tx_syncp);
                }
        }
-
+out:
        return !!budget;
 }