linux-kernel - printk NMI splat on boot

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Message-ID: <a93e1a96-3685-41c3-8979-472b20dfca14@kernel.dk>
Date: Tue, 20 May 2025 10:38:56 -0600
From: Jens Axboe <axboe@...nel.dk>
To: LKML <linux-kernel@...r.kernel.org>
Cc: Petr Mladek <pmladek@...e.com>, Steven Rostedt <rostedt@...dmis.org>,
 john.ogness@...utronix.de,
 "senozhatsky@...omium.org" <senozhatsky@...omium.org>
Subject: printk NMI splat on boot

Hi,

This has been going on for a while, and finally getting around to
reporting it. For every boot on my Dell R7625, I get one of these:

bnxt_en 0000:01:00.2 eno12419np2: renamed from eth2
usb 1-1.2: new low-speed USB device number 3 using xhci_hcd
usb 1-1.2: New USB device found, idVendor=047b, idProduct=0011, bcdDevice= 1.00
usb 3-1: New USB device found, idVendor=1604, idProduct=10c0, bcdDevice= 0.00
usb 1-1.2: New USB device strings: Mfr=1, Product=2, SerialNumber=0
rcu: INFO: rcu_sched detected expedited stalls on CPUs/tasks: { 96-.... } 3 jiffies s: 53 root: 0x40/.
rcu: blocking rcu_node structures (internal RCU debug): l=1:96-111:0x1/.
Sending NMI from CPU 0 to CPUs 96:
NMI backtrace for cpu 96
CPU: 96 UID: 0 PID: 3241 Comm: kworker/96:1 Not tainted 6.15.0-rc7+ #254 NONE 
Hardware name: Dell Inc. PowerEdge R7625/06444F, BIOS 1.11.2 12/18/2024
Workqueue: usb_hub_wq hub_event [usbcore]
RIP: 0010:vprintk_emit+0x360/0x430
Code: 87 01 0f 84 91 00 00 00 c6 05 36 ec 8a 01 01 c6 05 3c ec 8a 01 00 0f b6 05 28 ec 8a 01 84 c0 74 0d f3 90 0f b6 05 1b ec 8a 01 <84> c0 75 f3 e8 47 0d 00 00 80 e7 02 74 01 fb c7 05 bb ec 8c 01 00
RSP: 0018:ffffbe47220c7b78 EFLAGS: 00000002
RAX: 0000000000000001 RBX: 0000000000000246 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000002 RDI: ffffffff93019c48
RBP: ffffbe47220c7c48 R08: 00000000fffdffff R09: ffffa1bf658fffa8
R10: ffffa1bf64e00000 R11: 0000000000000002 R12: ffffbe47220c7be0
R13: ffffffff9260f8ee R14: ffffbe47220c7c58 R15: 0000000000000043
FS:  0000000000000000(0000) GS:ffffa14dd4a34000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000561066512398 CR3: 00000090a0a11002 CR4: 0000000000370ef0
Call Trace:
 <TASK>
 dev_vprintk_emit+0x130/0x140
 dev_printk_emit+0x3e/0x40
 ? __dev_printk+0x2d/0x70
 _dev_info+0x5c/0x5e
 usb_new_device.cold+0x87/0x3a0 [usbcore]
 hub_event+0x1113/0x1900 [usbcore]
 ? __schedule+0x4e5/0xaf0
 process_one_work+0x140/0x2b0
 worker_thread+0x2ea/0x430
 ? process_one_work+0x2b0/0x2b0
 kthread+0xd4/0x1d0
 ? kthreads_online_cpu+0xf0/0xf0
 ret_from_fork+0x2d/0x50
 ? kthreads_online_cpu+0xf0/0xf0
 ret_from_fork_asm+0x11/0x20
 </TASK>
usb 3-1: New USB device strings: Mfr=0, Product=0, SerialNumber=0
usb 1-1.2: Product: Standard USB Keyboard 
hub 3-1:1.0: USB hub found
usb 1-1.2: Manufacturer: Silitek

which appears to be this spin section:

        /* We spin waiting for the owner to release us */
        spin_acquire(&console_owner_dep_map, 0, 0, _THIS_IP_);
        /* Owner will clear console_waiter on hand off */
        while (READ_ONCE(console_waiter))
                cpu_relax();
        spin_release(&console_owner_dep_map, _THIS_IP_);

Box is a 2-socket, with 2:

AMD EPYC 9754 128-Core Processor

CPUs installed.

-- 
Jens Axboe