netdev - Re: [PATCH net-next] net: Add lockdep asserts to ____napi

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Date:   Thu, 17 Mar 2022 12:21:45 -0700
From:   Saeed Mahameed <saeed@...nel.org>
To:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc:     netdev@...r.kernel.org, "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH net-next] net: Add lockdep asserts to ____napi_schedule().

On 11 Mar 16:03, Sebastian Andrzej Siewior wrote:
>____napi_schedule() needs to be invoked with disabled interrupts due to
>__raise_softirq_irqoff (in order not to corrupt the per-CPU list).

This patch is likely causing the following call trace when RPS is enabled:

  [  690.429122] WARNING: CPU: 0 PID: 0 at net/core/dev.c:4268 rps_trigger_softirq+0x21/0xb0
  [  690.431236] Modules linked in: bonding ib_ipoib ipip tunnel4 geneve ib_umad ip6_gre ip6_tunnel tunnel6 rdma_ucm nf_tables ip_gre gre mlx5_ib ib_uverbs mlx5_core iptable_raw openvswitch nsh xt_conntrack xt_MASQUERADE nf_conntrack_netlink nfnetlink rpcrdma ib_iser xt_addrtype libiscsi scsi_transport_iscsi rdma_cm iw_cm iptable_nat nf_nat ib_cm br_netfilter ib_core overlay fuse [last unloaded: ib_uverbs]
  [  690.439693] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.17.0-rc7_net_next_4303f9c #1
  [  690.441709] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.13.0-0-gf21b5a4aeb02-prebuilt.qemu.org 04/01/2014
  [  690.444587] RIP: 0010:rps_trigger_softirq+0x21/0xb0
  [  690.445971] Code: ff 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 8b 05 b1 ea 21 01 53 48 89 fb 85 c0 74 1b 65 8b 05 16 56 71 7e a9 00 ff 0f 00 75 02 <0f> 0b 65 8b 05 4e 5f 72 7e 85 c0 74 5b 48 8b 83 e0 01 00 00 f6 c4
  [  690.450682] RSP: 0018:ffffffff82803e70 EFLAGS: 00010046
  [  690.452106] RAX: 0000000000000001 RBX: ffff88852ca3d400 RCX: ffff88852ca3d540
  [  690.453972] RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffff88852ca3d400
  [  690.455860] RBP: 0000000000000000 R08: ffff88852ca3d400 R09: 0000000000000001
  [  690.457684] R10: 0000000000000001 R11: 0000000000000000 R12: 0000000000000000
  [  690.459548] R13: ffff88852ca3d540 R14: ffffffff82829628 R15: 0000000000000000
  [  690.461429] FS:  0000000000000000(0000) GS:ffff88852ca00000(0000) knlGS:0000000000000000
  [  690.463653] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
  [  690.465180] CR2: 00007ff718200b98 CR3: 000000013b4de003 CR4: 0000000000370eb0
  [  690.467022] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
  [  690.468915] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
  [  690.470742] Call Trace:
  [  690.471544]  <TASK>
  [  690.472242]  flush_smp_call_function_queue+0xe5/0x1e0
  [  690.473639]  flush_smp_call_function_from_idle+0x5f/0xa0


For some reason - that i haven't looked into yet -
net_rps_send_ipi() will eventually ____napi_schedule()
only after enabling IRQ. see net_rps_action_and_irq_enable()