[syzbot] [kernel?] INFO: task hung in mmc_stop_host
From: syzbot
Date: Mon Aug 24 2026 - 20:04:26 EST
Hello,
syzbot found the following issue on:
HEAD commit: 388b607d107c Merge tag 'efi-next-for-v7.3' of git://git.ke..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1519c625580000
kernel config: https://syzkaller.appspot.com/x/.config?x=335632b21d0ce540
dashboard link: https://syzkaller.appspot.com/bug?extid=d0688023306aea3aefdc
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/20c420e92df0/disk-388b607d.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/82f836a86dcc/vmlinux-388b607d.xz
kernel image: https://storage.googleapis.com/syzbot-assets/c3b00ac47be8/bzImage-388b607d.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d0688023306aea3aefdc@xxxxxxxxxxxxxxxxxxxxxxxxx
INFO: task kworker/0:4:1939 blocked for more than 143 seconds.
Tainted: G L syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/0:4 state:D stack:21280 pid:1939 tgid:1939 ppid:2 task_flags:0x4288060 flags:0x00080000
Workqueue: usb_hub_wq hub_event
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5520 [inline]
__schedule+0x17d4/0x5820 kernel/sched/core.c:7270
__schedule_loop kernel/sched/core.c:7347 [inline]
schedule+0x164/0x2b0 kernel/sched/core.c:7362
schedule_timeout+0xc0/0x2c0 kernel/time/sleep_timeout.c:75
do_wait_for_common kernel/sched/completion.c:100 [inline]
__wait_for_common kernel/sched/completion.c:121 [inline]
wait_for_common kernel/sched/completion.c:132 [inline]
wait_for_completion+0x2ca/0x5e0 kernel/sched/completion.c:153
__flush_work+0xa63/0xca0 kernel/workqueue.c:4439
__cancel_work_sync+0xbf/0x110 kernel/workqueue.c:4559
__mmc_stop_host drivers/mmc/core/core.c:2368 [inline]
mmc_stop_host+0xd9/0x460 drivers/mmc/core/core.c:2373
mmc_remove_host+0x15/0x60 drivers/mmc/core/host.c:681
vub300_disconnect+0x154/0x2f0 drivers/mmc/host/vub300.c:2387
usb_unbind_interface+0x295/0x9f0 drivers/usb/core/driver.c:458
device_remove drivers/base/dd.c:618 [inline]
__device_release_driver drivers/base/dd.c:1349 [inline]
device_release_driver_internal+0x4f5/0x880 drivers/base/dd.c:1372
bus_remove_device+0x444/0x560 drivers/base/bus.c:664
device_del+0x524/0x8f0 drivers/base/core.c:3965
usb_disable_device+0x3d4/0x8d0 drivers/usb/core/message.c:1478
usb_disconnect+0x346/0x9a0 drivers/usb/core/hub.c:2345
hub_port_connect drivers/usb/core/hub.c:5415 [inline]
hub_port_connect_change drivers/usb/core/hub.c:5715 [inline]
port_event drivers/usb/core/hub.c:5879 [inline]
hub_event+0x1bbb/0x4d30 drivers/usb/core/hub.c:5961
process_one_work kernel/workqueue.c:3387 [inline]
process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3470
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3551
kthread+0x38b/0x480 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
INFO: task kworker/0:8:1944 blocked for more than 143 seconds.
Tainted: G L syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/0:8 state:D stack:21512 pid:1944 tgid:1944 ppid:2 task_flags:0x4208060 flags:0x00080000
Workqueue: events_freezable mmc_rescan
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5520 [inline]
__schedule+0x17d4/0x5820 kernel/sched/core.c:7270
__schedule_loop kernel/sched/core.c:7347 [inline]
schedule+0x164/0x2b0 kernel/sched/core.c:7362
schedule_timeout+0xc0/0x2c0 kernel/time/sleep_timeout.c:75
do_wait_for_common kernel/sched/completion.c:100 [inline]
__wait_for_common kernel/sched/completion.c:121 [inline]
wait_for_common kernel/sched/completion.c:132 [inline]
wait_for_completion+0x2ca/0x5e0 kernel/sched/completion.c:153
mmc_wait_for_req_done+0x37/0x490 drivers/mmc/core/core.c:408
mmc_wait_for_cmd+0x183/0x2a0 drivers/mmc/core/core.c:645
mmc_io_rw_direct_host drivers/mmc/core/sdio_ops.c:83 [inline]
sdio_reset+0xf4/0x3a0 drivers/mmc/core/sdio_ops.c:209
mmc_rescan_try_freq drivers/mmc/core/core.c:2121 [inline]
mmc_rescan+0x6eb/0x1040 drivers/mmc/core/core.c:2316
process_one_work kernel/workqueue.c:3387 [inline]
process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3470
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3551
kthread+0x38b/0x480 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Showing all locks held in the system:
locks held by khungtaskd/31: 1, last CPU#1:
#0: ffffffff8ed5a420 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#0: ffffffff8ed5a420 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
#0: ffffffff8ed5a420 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x2e/0x180 kernel/locking/lockdep.c:6793
locks held by getty/5366: 2, on CPU#1:
#0: ffff8880364560a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc900032332e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x45a/0x1360 drivers/tty/n_tty.c:2211
locks held by kworker/0:4/1939: 5, on CPU#0:
#0: ffff88801eaa2d40 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#0: ffff88801eaa2d40 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
#0: ffff88801eaa2d40 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3352 [inline]
#0: ffff88801eaa2d40 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3470
#1: ffffc90003e7fc40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#1: ffffc90003e7fc40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
#1: ffffc90003e7fc40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3352 [inline]
#1: ffffc90003e7fc40 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3470
#2: ffff8880265631d8 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:1104 [inline]
#2: ffff8880265631d8 (&dev->mutex){....}-{4:4}, at: hub_event+0x184/0x4d30 drivers/usb/core/hub.c:5907
#3: ffff8880677ae1d8 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:1104 [inline]
#3: ffff8880677ae1d8 (&dev->mutex){....}-{4:4}, at: usb_disconnect+0xfc/0x9a0 drivers/usb/core/hub.c:2336
#4: ffff888053cc71a0 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:1104 [inline]
#4: ffff888053cc71a0 (&dev->mutex){....}-{4:4}, at: __device_driver_lock drivers/base/dd.c:1171 [inline]
#4: ffff888053cc71a0 (&dev->mutex){....}-{4:4}, at: device_release_driver_internal+0xb9/0x880 drivers/base/dd.c:1369
locks held by kworker/0:8/1944: 2, on CPU#0:
#0: ffff88801b06a140 ((wq_completion)events_freezable){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#0: ffff88801b06a140 ((wq_completion)events_freezable){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
#0: ffff88801b06a140 ((wq_completion)events_freezable){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3352 [inline]
#0: ffff88801b06a140 ((wq_completion)events_freezable){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3470
#1: ffffc90003b4fc40 ((work_completion)(&(&host->detect)->work)){+.+.}-{0:0}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#1: ffffc90003b4fc40 ((work_completion)(&(&host->detect)->work)){+.+.}-{0:0}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
#1: ffffc90003b4fc40 ((work_completion)(&(&host->detect)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3352 [inline]
#1: ffffc90003b4fc40 ((work_completion)(&(&host->detect)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x97a/0x1630 kernel/workqueue.c:3470
=============================================
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 31 Comm: khungtaskd Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
nmi_cpu_backtrace+0x274/0x2d0 lib/nmi_backtrace.c:123
nmi_trigger_cpumask_backtrace+0x17d/0x390 lib/nmi_backtrace.c:66
trigger_all_cpu_backtrace include/linux/nmi.h:164 [inline]
__sys_info lib/sys_info.c:157 [inline]
sys_info+0x135/0x170 lib/sys_info.c:165
check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
watchdog+0xfd7/0x1030 kernel/hung_task.c:561
kthread+0x38b/0x480 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 1002 Comm: kworker/u8:6 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue: events_unbound toggle_allocation_gate
RIP: 0010:mark_usage kernel/locking/lockdep.c:4636 [inline]
RIP: 0010:__lock_acquire+0x5d5/0x2cf0 kernel/locking/lockdep.c:5207
Code: fe e8 4f 88 76 03 e9 69 ff ff ff 44 89 e0 38 44 24 10 76 16 e8 5c 86 35 03 85 c0 74 0d 83 3d 95 3d d7 0e 00 0f 84 93 07 00 00 <85> ed 0f 84 96 00 00 00 41 8b 45 20 66 85 c0 78 7e 65 8b 0d af 51
RSP: 0018:ffffc900051575b8 EFLAGS: 00000046
RAX: 0000000000000004 RBX: ffff888028192ba8 RCX: 0000000000000004
RDX: 0000000000000004 RSI: 0000000000000005 RDI: 0000000000000000
RBP: 0000000000000001 R08: ffffffff816ac8cf R09: 0000000000000000
R10: 0000000000000000 R11: ffffffff8ebfd3a0 R12: 0000000000000004
R13: ffff888028192b88 R14: ffff888028191f40 R15: 0000000000000004
FS: 0000000000000000(0000) GS:ffff888124df4000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c359880 CR3: 000000000eb46000 CR4: 00000000003526f0
Call Trace:
<TASK>
lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5886
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
arch_jump_label_transform_queue+0x5f/0x110 arch/x86/kernel/jump_label.c:136
__jump_label_update+0x189/0x370 kernel/jump_label.c:513
static_key_disable_cpuslocked+0xc5/0x1a0 kernel/jump_label.c:240
static_key_disable+0x1a/0x20 kernel/jump_label.c:248
toggle_allocation_gate+0x1fe/0x290 mm/kfence/core.c:918
process_one_work kernel/workqueue.c:3387 [inline]
process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3470
worker_thread+0xa47/0xfb0 kernel/workqueue.c:3551
kthread+0x38b/0x480 kernel/kthread.c:436
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
---
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