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Date:   Tue, 9 Feb 2021 12:29:42 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc:     Paul McKenney <paulmck@kernel.org>,
        Linux PM <linux-pm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Frederic Weisbecker <frederic@kernel.org>,
        kvalo@codeaurora.org, johannes@sipsolutions.net
Subject: Re: WARNING: suspicious RCU usage (5.11.0-rc7+ #1812 Tainted: G)
Message-ID: <YCJyJgEeiQqBRgzL@hirez.programming.kicks-ass.net>
References: <2578278.ATerS0GEoy@kreacher>
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In-Reply-To: <2578278.ATerS0GEoy@kreacher>
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On Mon, Feb 08, 2021 at 08:04:27PM +0100, Rafael J. Wysocki wrote:
> Hi Peter & Paul,
> 
> The traces below are present in the boot dmesg log on my Dell XPS13 9360.
> 
> I haven't had the time to look into this in detail yet, but here it goes in
> case you know what's going on already.
> 
> Cheers!
> 
> 
> [   86.762542] IPv6: ADDRCONF(NETDEV_CHANGE): wlan0: link becomes ready
> 
> [   86.764298] =============================
> [   86.764300] WARNING: suspicious RCU usage
> [   86.764302] 5.11.0-rc7+ #1812 Tainted: G          I      
> [   86.764305] -----------------------------
> [   86.764307] /scratch/rafael/work/linux-pm/include/linux/rhashtable.h:594 suspicious rcu_dereference_check() usage!
> [   86.764309] 
>                other info that might help us debug this:
> 
> [   86.764311] 
>                rcu_scheduler_active = 2, debug_locks = 1
> [   86.764313] no locks held by swapper/1/0.
> [   86.764316] 
>                stack backtrace:
> [   86.764318] CPU: 1 PID: 0 Comm: swapper/1 Tainted: G          I       5.11.0-rc7+ #1812
> [   86.764321] Hardware name: Dell Inc. XPS 13 9360/, BIOS 1.3.5 05/08/2017
> [   86.764323] Call Trace:
> [   86.764325]  <IRQ>
> [   86.764328]  dump_stack+0x77/0x97
> [   86.764336]  ieee80211_find_sta_by_ifaddr+0x218/0x2e0 [mac80211]
> [   86.764380]  ? ath10k_wmi_tlv_op_pull_mgmt_tx_bundle_compl_ev+0xe0/0xe0 [ath10k_core]
> [   86.764399]  ath10k_wmi_tlv_parse_peer_stats_info+0x2a/0x70 [ath10k_core]
> [   86.764411]  ath10k_wmi_tlv_iter+0x56/0xd0 [ath10k_core]
> [   86.764424]  ath10k_wmi_tlv_op_rx+0x75a/0xa30 [ath10k_core]
> [   86.764438]  ath10k_htc_rx_completion_handler+0xe8/0x120 [ath10k_core]
> [   86.764452]  ? ath10k_htc_process_trailer+0x290/0x290 [ath10k_core]
> [   86.764462]  ath10k_pci_process_rx_cb+0x117/0x180 [ath10k_pci]
> [   86.764472]  ? ath10k_ce_per_engine_service+0x4c/0x80 [ath10k_core]
> [   86.764490]  ? _raw_spin_unlock_irqrestore+0x47/0x60
> [   86.764504]  ath10k_ce_per_engine_service+0x5d/0x80 [ath10k_core]
> [   86.764524]  ath10k_ce_per_engine_service_any+0x6a/0xa0 [ath10k_core]
> [   86.764543]  ath10k_pci_napi_poll+0x44/0x110 [ath10k_pci]
> [   86.764552]  net_rx_action+0x15d/0x4e0
> [   86.764570]  __do_softirq+0xeb/0x492
> [   86.764583]  ? handle_fasteoi_irq+0x150/0x150
> [   86.764591]  asm_call_irq_on_stack+0x12/0x20
> [   86.764598]  </IRQ>
> [   86.764602]  do_softirq_own_stack+0x81/0xa0
> [   86.764609]  irq_exit_rcu+0xcd/0xe0
> [   86.764614]  common_interrupt+0xfe/0x230
> [   86.764623]  asm_common_interrupt+0x1e/0x40
> [   86.764626] RIP: 0010:cpuidle_enter_state+0x109/0x4a0
> [   86.764631] Code: 02 00 00 31 ff e8 b7 40 8e ff 45 84 ff 74 12 9c 58 f6 c4 02 0f 85 10 03 00 00 31 ff e8 70 42 96 ff e8 bb a2 9d ff fb 45 85 f6 <0f> 88 12 01 00 00 49 63 d6 4c 2b 24 24 48 8d 04 52 48 8d 04 82 49
> [   86.764634] RSP: 0018:ffffc900000e3e80 EFLAGS: 00000202
> [   86.764638] RAX: 00000000000e8d89 RBX: 0000000000000002 RCX: 0000000000000000
> [   86.764641] RDX: 0000000000000000 RSI: ffffffff82392561 RDI: ffffffff82344126
> [   86.764643] RBP: ffffe8ffffc93300 R08: 0000000000000001 R09: 0000000000000001
> [   86.764645] R10: ffffc900000e3e60 R11: 0000000000000002 R12: 00000014338d5797
> [   86.764647] R13: ffffffff827e6d60 R14: 0000000000000002 R15: 0000000000000000
> [   86.764667]  cpuidle_enter+0x29/0x40
> [   86.764672]  do_idle+0x22d/0x2b0
> [   86.764682]  cpu_startup_entry+0x19/0x20
> [   86.764686]  start_secondary+0x125/0x160
> [   86.764691]  secondary_startup_64_no_verify+0xb0/0xbb
> 

AFAICT that's a simple 'use RCU without holding rcu_read_lock' warning.
I've not dug through ath10k to see who should be doing rcu_read_lock,
but the few places I did look at don't seem to have changed recently.