[syzbot ci] Re: mm/vmalloc: use dedicated unbound workqueue for vmap area draining

syzbot ci
2026-03-20T09:51:25Z

syzbot ci has tested the following series

[v2] mm/vmalloc: use dedicated unbound workqueue for vmap area draining
https://lore.kernel.org/all/20260319074307.2325-1-lirongqing@baidu.com
* [PATCH v2] mm/vmalloc: use dedicated unbound workqueue for vmap area draining

and found the following issue:
possible deadlock in console_flush_all

Full report is available here:
https://ci.syzbot.org/series/1703e204-a8b3-43ef-8979-a596c0ada77b

***

possible deadlock in console_flush_all

tree: mm-new
URL: https://kernel.googlesource.com/pub/scm/linux/kernel/git/akpm/mm.git
base: 8616acb9dc887e0e271229bf520b5279fbd22f94
arch: amd64
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
config: https://ci.syzbot.org/builds/b3a95cb5-d858-4555-a40b-1b611b74214b/config
syz repro: https://ci.syzbot.org/findings/d4780575-25c4-4403-a24b-e1c9a6237f30/syz_repro

------------[ cut here ]------------
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
kworker/u9:4/94 is trying to acquire lock:
ffffffff8e750900 (console_owner){....}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:317 [inline]
ffffffff8e750900 (console_owner){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:428 [inline]
ffffffff8e750900 (console_owner){....}-{0:0}, at: console_srcu_read_lock kernel/printk/printk.c:291 [inline]
ffffffff8e750900 (console_owner){....}-{0:0}, at: console_flush_one_record kernel/printk/printk.c:3246 [inline]
ffffffff8e750900 (console_owner){....}-{0:0}, at: console_flush_all+0x123/0xb20 kernel/printk/printk.c:3343

but task is already holding lock:
ffff88812103a498 (&pool->lock){-.-.}-{2:2}, at: start_flush_work kernel/workqueue.c:4241 [inline]
ffff88812103a498 (&pool->lock){-.-.}-{2:2}, at: __flush_work+0x1ef/0xc50 kernel/workqueue.c:4292

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #3 (&pool->lock){-.-.}-{2:2}:
__raw_spin_lock include/linux/spinlock_api_smp.h:158 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
__queue_work+0x80b/0x1020 kernel/workqueue.c:-1
queue_work_on+0x106/0x1d0 kernel/workqueue.c:2405
queue_work include/linux/workqueue.h:669 [inline]
rpm_suspend+0xe85/0x1750 drivers/base/power/runtime.c:688
__pm_runtime_idle+0x12f/0x1a0 drivers/base/power/runtime.c:1129
pm_runtime_put include/linux/pm_runtime.h:551 [inline]
__device_attach+0x34f/0x450 drivers/base/dd.c:1051
device_initial_probe+0xa1/0xd0 drivers/base/dd.c:1088
bus_probe_device+0x12a/0x220 drivers/base/bus.c:574
device_add+0x7b6/0xb70 drivers/base/core.c:3689
serial_base_port_add+0x18f/0x260 drivers/tty/serial/serial_base_bus.c:186
serial_core_port_device_add drivers/tty/serial/serial_core.c:3257 [inline]
serial_core_register_port+0x375/0x28a0 drivers/tty/serial/serial_core.c:3296
serial8250_register_8250_port+0x1658/0x1fd0 drivers/tty/serial/8250/8250_core.c:822
serial_pnp_probe+0x568/0x7f0 drivers/tty/serial/8250/8250_pnp.c:480
pnp_device_probe+0x30b/0x4c0 drivers/pnp/driver.c:111
call_driver_probe drivers/base/dd.c:-1 [inline]
really_probe+0x267/0xaf0 drivers/base/dd.c:661
__driver_probe_device+0x18c/0x320 drivers/base/dd.c:803
driver_probe_device+0x4f/0x240 drivers/base/dd.c:833
__driver_attach+0x349/0x640 drivers/base/dd.c:1227
bus_for_each_dev+0x23b/0x2c0 drivers/base/bus.c:383
bus_add_driver+0x345/0x670 drivers/base/bus.c:715
driver_register+0x23a/0x320 drivers/base/driver.c:249
serial8250_init+0x8f/0x160 drivers/tty/serial/8250/8250_platform.c:317
do_one_initcall+0x250/0x8d0 init/main.c:1383
do_initcall_level+0x104/0x190 init/main.c:1445
do_initcalls+0x59/0xa0 init/main.c:1461
kernel_init_freeable+0x2a6/0x3e0 init/main.c:1693
kernel_init+0x1d/0x1d0 init/main.c:1583
ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

-> #2 (&dev->power.lock){-...}-{3:3}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline]
_raw_spin_lock_irqsave+0x40/0x60 kernel/locking/spinlock.c:162
__pm_runtime_resume+0x10f/0x180 drivers/base/power/runtime.c:1196
pm_runtime_get include/linux/pm_runtime.h:494 [inline]
__uart_start+0x171/0x460 drivers/tty/serial/serial_core.c:149
uart_write+0x265/0xa10 drivers/tty/serial/serial_core.c:633
process_output_block drivers/tty/n_tty.c:557 [inline]
n_tty_write+0xd84/0x12a0 drivers/tty/n_tty.c:2366
iterate_tty_write drivers/tty/tty_io.c:1006 [inline]
file_tty_write+0x559/0xa20 drivers/tty/tty_io.c:1081
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x61d/0xb90 fs/read_write.c:688
ksys_write+0x150/0x270 fs/read_write.c:740
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x14d/0xf80 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (&port_lock_key){-...}-{3:3}:
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:132 [inline]
_raw_spin_lock_irqsave+0x40/0x60 kernel/locking/spinlock.c:162
uart_port_lock_irqsave include/linux/serial_core.h:717 [inline]
serial8250_console_write+0x150/0x1ba0 drivers/tty/serial/8250/8250_port.c:3301
console_emit_next_record kernel/printk/printk.c:3183 [inline]
console_flush_one_record kernel/printk/printk.c:3269 [inline]
console_flush_all+0x718/0xb20 kernel/printk/printk.c:3343
__console_flush_and_unlock kernel/printk/printk.c:3373 [inline]
console_unlock+0xd1/0x1c0 kernel/printk/printk.c:3413
vprintk_emit+0x485/0x560 kernel/printk/printk.c:2479
_printk+0xdd/0x130 kernel/printk/printk.c:2504
register_console+0xbc2/0xfa0 kernel/printk/printk.c:4208
univ8250_console_init+0x3a/0x70 drivers/tty/serial/8250/8250_core.c:515
console_init+0x10b/0x4d0 kernel/printk/printk.c:4407
start_kernel+0x230/0x3e0 init/main.c:1148
x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
x86_64_start_kernel+0x143/0x1c0 arch/x86/kernel/head64.c:291
common_startup_64+0x13e/0x147

-> #0 (console_owner){....}-{0:0}:
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain kernel/locking/lockdep.c:3908 [inline]
__lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
console_lock_spinning_enable kernel/printk/printk.c:1902 [inline]
console_emit_next_record kernel/printk/printk.c:3177 [inline]
console_flush_one_record kernel/printk/printk.c:3269 [inline]
console_flush_all+0x6c1/0xb20 kernel/printk/printk.c:3343
__console_flush_and_unlock kernel/printk/printk.c:3373 [inline]
console_unlock+0xd1/0x1c0 kernel/printk/printk.c:3413
vprintk_emit+0x485/0x560 kernel/printk/printk.c:2479
_printk+0xdd/0x130 kernel/printk/printk.c:2504
__report_bug+0x317/0x540 lib/bug.c:243
report_bug_entry+0x19a/0x290 lib/bug.c:269
handle_bug+0xce/0x200 arch/x86/kernel/traps.c:430
exc_invalid_op+0x1a/0x50 arch/x86/kernel/traps.c:489
asm_exc_invalid_op+0x1a/0x20 arch/x86/include/asm/idtentry.h:616
check_flush_dependency+0x312/0x3c0 kernel/workqueue.c:3801
start_flush_work kernel/workqueue.c:4255 [inline]
__flush_work+0x411/0xc50 kernel/workqueue.c:4292
__purge_vmap_area_lazy+0x876/0xb70 mm/vmalloc.c:2412
drain_vmap_area_work+0x27/0x40 mm/vmalloc.c:2437
process_one_work kernel/workqueue.c:3276 [inline]
process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

other info that might help us debug this:

Chain exists of:
console_owner --> &dev->power.lock --> &pool->lock

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&pool->lock);
lock(&dev->power.lock);
lock(&pool->lock);
lock(console_owner);

*** DEADLOCK ***

7 locks held by kworker/u9:4/94:
#0: ffff8881000ab948 ((wq_completion)vmap_drain){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3251 [inline]
#0: ffff8881000ab948 ((wq_completion)vmap_drain){+.+.}-{0:0}, at: process_scheduled_works+0xa52/0x18c0 kernel/workqueue.c:3359
#1: ffffc9000289fc40 (drain_vmap_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3252 [inline]
#1: ffffc9000289fc40 (drain_vmap_work){+.+.}-{0:0}, at: process_scheduled_works+0xa8d/0x18c0 kernel/workqueue.c:3359
#2: ffffffff8e87ec08 (vmap_purge_lock){+.+.}-{4:4}, at: drain_vmap_area_work+0x17/0x40 mm/vmalloc.c:2436
#3: ffffffff8e75e520 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:312 [inline]
#3: ffffffff8e75e520 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:850 [inline]
#3: ffffffff8e75e520 (rcu_read_lock){....}-{1:3}, at: start_flush_work kernel/workqueue.c:4234 [inline]
#3: ffffffff8e75e520 (rcu_read_lock){....}-{1:3}, at: __flush_work+0x100/0xc50 kernel/workqueue.c:4292
#4: ffff88812103a498 (&pool->lock){-.-.}-{2:2}, at: start_flush_work kernel/workqueue.c:4241 [inline]
#4: ffff88812103a498 (&pool->lock){-.-.}-{2:2}, at: __flush_work+0x1ef/0xc50 kernel/workqueue.c:4292
#5: ffffffff8e750960 (console_lock){+.+.}-{0:0}, at: _printk+0xdd/0x130 kernel/printk/printk.c:2504
#6: ffffffff8e638218 (console_srcu){....}-{0:0}, at: rcu_try_lock_acquire include/linux/rcupdate.h:317 [inline]
#6: ffffffff8e638218 (console_srcu){....}-{0:0}, at: srcu_read_lock_nmisafe include/linux/srcu.h:428 [inline]
#6: ffffffff8e638218 (console_srcu){....}-{0:0}, at: console_srcu_read_lock kernel/printk/printk.c:291 [inline]
#6: ffffffff8e638218 (console_srcu){....}-{0:0}, at: console_flush_one_record kernel/printk/printk.c:3246 [inline]
#6: ffffffff8e638218 (console_srcu){....}-{0:0}, at: console_flush_all+0x123/0xb20 kernel/printk/printk.c:3343

stack backtrace:
CPU: 0 UID: 0 PID: 94 Comm: kworker/u9:4 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Workqueue: vmap_drain drain_vmap_area_work
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain kernel/locking/lockdep.c:3908 [inline]
__lock_acquire+0x15a5/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0xf0/0x2e0 kernel/locking/lockdep.c:5868
console_lock_spinning_enable kernel/printk/printk.c:1902 [inline]
console_emit_next_record kernel/printk/printk.c:3177 [inline]
console_flush_one_record kernel/printk/printk.c:3269 [inline]
console_flush_all+0x6c1/0xb20 kernel/printk/printk.c:3343
__console_flush_and_unlock kernel/printk/printk.c:3373 [inline]
console_unlock+0xd1/0x1c0 kernel/printk/printk.c:3413
vprintk_emit+0x485/0x560 kernel/printk/printk.c:2479
_printk+0xdd/0x130 kernel/printk/printk.c:2504
__report_bug+0x317/0x540 lib/bug.c:243
report_bug_entry+0x19a/0x290 lib/bug.c:269
handle_bug+0xce/0x200 arch/x86/kernel/traps.c:430
exc_invalid_op+0x1a/0x50 arch/x86/kernel/traps.c:489
asm_exc_invalid_op+0x1a/0x20 arch/x86/include/asm/idtentry.h:616
RIP: 0010:check_flush_dependency+0x312/0x3c0 kernel/workqueue.c:3801
Code: 00 00 fc ff df 80 3c 08 00 74 08 4c 89 f7 e8 f5 33 a2 00 49 8b 16 48 81 c3 78 01 00 00 4c 89 ef 4c 89 e6 48 89 d9 4c 8b 04 24 <67> 48 0f b9 3a e9 53 ff ff ff 44 89 f1 80 e1 07 80 c1 03 38 c1 0f
RSP: 0018:ffffc9000289f860 EFLAGS: 00010086
RAX: 1ffff110202e9103 RBX: ffff88810006b178 RCX: ffff88810006b178
RDX: ffffffff821ed1f0 RSI: ffff8881000ab978 RDI: ffffffff9014a330
RBP: ffff888100687008 R08: ffffffff821ee110 R09: 1ffff1102000fb21
R10: dffffc0000000000 R11: ffffed102000fb22 R12: ffff8881000ab978
R13: ffffffff9014a330 R14: ffff888101748818 R15: ffff888101748820
start_flush_work kernel/workqueue.c:4255 [inline]
__flush_work+0x411/0xc50 kernel/workqueue.c:4292
__purge_vmap_area_lazy+0x876/0xb70 mm/vmalloc.c:2412
drain_vmap_area_work+0x27/0x40 mm/vmalloc.c:2437
process_one_work kernel/workqueue.c:3276 [inline]
process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
workqueue: WQ_MEM_RECLAIM vmap_drain:drain_vmap_area_work is flushing !WQ_MEM_RECLAIM events:purge_vmap_node
WARNING: kernel/workqueue.c:3805 at check_flush_dependency+0x28f/0x3c0 kernel/workqueue.c:3801, CPU#0: kworker/u9:4/94
Modules linked in:
CPU: 0 UID: 0 PID: 94 Comm: kworker/u9:4 Not tainted syzkaller #0 PREEMPT(full)
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Workqueue: vmap_drain drain_vmap_area_work
RIP: 0010:check_flush_dependency+0x312/0x3c0 kernel/workqueue.c:3801
Code: 00 00 fc ff df 80 3c 08 00 74 08 4c 89 f7 e8 f5 33 a2 00 49 8b 16 48 81 c3 78 01 00 00 4c 89 ef 4c 89 e6 48 89 d9 4c 8b 04 24 <67> 48 0f b9 3a e9 53 ff ff ff 44 89 f1 80 e1 07 80 c1 03 38 c1 0f
RSP: 0018:ffffc9000289f860 EFLAGS: 00010086
RAX: 1ffff110202e9103 RBX: ffff88810006b178 RCX: ffff88810006b178
RDX: ffffffff821ed1f0 RSI: ffff8881000ab978 RDI: ffffffff9014a330
RBP: ffff888100687008 R08: ffffffff821ee110 R09: 1ffff1102000fb21
R10: dffffc0000000000 R11: ffffed102000fb22 R12: ffff8881000ab978
R13: ffffffff9014a330 R14: ffff888101748818 R15: ffff888101748820
FS: 0000000000000000(0000) GS:ffff88818de5e000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000386000 CR3: 0000000114a6a000 CR4: 00000000000006f0
Call Trace:
<TASK>
start_flush_work kernel/workqueue.c:4255 [inline]
__flush_work+0x411/0xc50 kernel/workqueue.c:4292
__purge_vmap_area_lazy+0x876/0xb70 mm/vmalloc.c:2412
drain_vmap_area_work+0x27/0x40 mm/vmalloc.c:2437
process_one_work kernel/workqueue.c:3276 [inline]
process_scheduled_works+0xb6e/0x18c0 kernel/workqueue.c:3359
worker_thread+0xa53/0xfc0 kernel/workqueue.c:3440
kthread+0x388/0x470 kernel/kthread.c:436
ret_from_fork+0x51e/0xb90 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
----------------
Code disassembly (best guess), 4 bytes skipped:
0: df 80 3c 08 00 74 filds 0x7400083c(%rax)
6: 08 4c 89 f7 or %cl,-0x9(%rcx,%rcx,4)
a: e8 f5 33 a2 00 call 0xa23404
f: 49 8b 16 mov (%r14),%rdx
12: 48 81 c3 78 01 00 00 add $0x178,%rbx
19: 4c 89 ef mov %r13,%rdi
1c: 4c 89 e6 mov %r12,%rsi
1f: 48 89 d9 mov %rbx,%rcx
22: 4c 8b 04 24 mov (%rsp),%r8
* 26: 67 48 0f b9 3a ud1 (%edx),%rdi <-- trapping instruction
2b: e9 53 ff ff ff jmp 0xffffff83
30: 44 89 f1 mov %r14d,%ecx
33: 80 e1 07 and $0x7,%cl
36: 80 c1 03 add $0x3,%cl
39: 38 c1 cmp %al,%cl
3b: 0f .byte 0xf

***

If these findings have caused you to resend the series or submit a
separate fix, please add the following tag to your commit message:
Tested-by: syzbot@syzkaller.appspotmail.com

---
This report is generated by a bot. It may contain errors.
syzbot ci engineers can be reached at syzkaller@googlegroups.com.