INFO: task hung in __rq_qos_throttle

Status: premoderation: reported C repro on 2026/08/23 14:30
Reported-by: syzbot+1fdff4cefa5756a4a3f4@syzkaller.appspotmail.com
First crash: 6d04h, last: 2d11h
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 INFO: task hung in __rq_qos_throttle 1 syz, C 4 22d 24d 0/3 upstream: reported C repro on 2026/08/05 16:53
upstream INFO: task hung in __rq_qos_throttle block 1 11 528d 707d 0/29 auto-obsoleted due to no activity on 2025/06/17 16:47
linux-6.6 INFO: task hung in __rq_qos_throttle 1 syz, C 3 6d06h 24d 0/2 upstream: reported C repro on 2026/08/05 05:35
upstream INFO: task hung in __rq_qos_throttle (2) prio:high block 1 syz, C 34 12h58m 20d 0/29 upstream: reported C repro on 2026/08/08 20:07
linux-5.15 INFO: task hung in __rq_qos_throttle 1 syz, C 6 7d00h 19d 0/3 upstream: reported C repro on 2026/08/10 12:40

Sample crash report:
INFO: task kworker/u8:0:12 blocked for more than 122 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/u8:0    state:D stack:0     pid:12    tgid:12    ppid:2      flags:0x00004000
Workqueue: writeback wb_workfn (flush-8:0)
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:6060 [inline]
 __schedule+0x1496/0x20b0 kernel/sched/core.c:7880
 __schedule_loop kernel/sched/core.c:7957 [inline]
 schedule+0xc5/0x240 kernel/sched/core.c:7972
 io_schedule+0x88/0xe0 kernel/sched/core.c:8786
 rq_qos_wait+0x252/0x330 block/blk-rq-qos.c:282
 __wbt_wait block/blk-wbt.c:594 [inline]
 wbt_wait+0x326/0x540 block/blk-wbt.c:658
 __rq_qos_throttle+0x7a/0xd0 block/blk-rq-qos.c:66
 rq_qos_throttle block/blk-rq-qos.h:151 [inline]
 blk_mq_get_new_requests block/blk-mq.c:3062 [inline]
 blk_mq_submit_bio+0xe6d/0x2130 block/blk-mq.c:3214
 __submit_bio+0x223/0x9b0 block/blk-core.c:635
 __submit_bio_noacct_mq block/blk-core.c:722 [inline]
 submit_bio_noacct_nocheck+0x43c/0xab0 block/blk-core.c:751
 submit_bio_noacct+0xc0e/0x1620 block/blk-core.c:874
 submit_bio+0x424/0x5b0 block/blk-core.c:949
 ext4_io_submit+0xe5/0x150 fs/ext4/page-io.c:389
 ext4_do_writepages+0x2741/0x39f0 fs/ext4/inode.c:2758
 ext4_writepages+0x28c/0x550 fs/ext4/inode.c:2827
 do_writepages+0x3d7/0x7f0 mm/page-writeback.c:2690
 __writeback_single_inode+0xc8/0xba0 fs/fs-writeback.c:1674
 writeback_sb_inodes+0x6a5/0xfb0 fs/fs-writeback.c:1970
 __writeback_inodes_wb+0x129/0x280 fs/fs-writeback.c:2041
 wb_writeback+0x3bb/0x850 fs/fs-writeback.c:2152
 wb_check_background_flush fs/fs-writeback.c:2222 [inline]
 wb_do_writeback fs/fs-writeback.c:2310 [inline]
 wb_workfn+0xab0/0xef0 fs/fs-writeback.c:2337
 process_one_work kernel/workqueue.c:3273 [inline]
 process_scheduled_works+0x7f7/0x1060 kernel/workqueue.c:3354
 worker_thread+0xc99/0x13f0 kernel/workqueue.c:3435
 kthread+0x2c7/0x360 kernel/kthread.c:389
 ret_from_fork+0x67/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
INFO: task jbd2/sda1-8:73 blocked for more than 123 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:jbd2/sda1-8     state:D stack:0     pid:73    tgid:73    ppid:2      flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:6060 [inline]
 __schedule+0x1496/0x20b0 kernel/sched/core.c:7880
 __schedule_loop kernel/sched/core.c:7957 [inline]
 schedule+0xc5/0x240 kernel/sched/core.c:7972
 io_schedule+0x88/0xe0 kernel/sched/core.c:8786
 bit_wait_io+0x17/0xd0 kernel/sched/wait_bit.c:209
 __wait_on_bit+0xb3/0x2e0 kernel/sched/wait_bit.c:49
 out_of_line_wait_on_bit+0x139/0x190 kernel/sched/wait_bit.c:64
 wait_on_bit_io include/linux/wait_bit.h:101 [inline]
 __wait_on_buffer+0x5a/0x70 fs/buffer.c:123
 wait_on_buffer include/linux/buffer_head.h:422 [inline]
 jbd2_journal_commit_transaction+0x2dba/0x5510 fs/jbd2/commit.c:814
 kjournald2+0x386/0x6a0 fs/jbd2/journal.c:201
 kthread+0x2c7/0x360 kernel/kthread.c:389
 ret_from_fork+0x67/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
INFO: task syz.1.442:826 blocked for more than 123 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.442       state:D stack:0     pid:826   tgid:826   ppid:381    flags:0x00000004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:6060 [inline]
 __schedule+0x1496/0x20b0 kernel/sched/core.c:7880
 __schedule_loop kernel/sched/core.c:7957 [inline]
 schedule+0xc5/0x240 kernel/sched/core.c:7972
 io_schedule+0x88/0xe0 kernel/sched/core.c:8786
 bit_wait_io+0x17/0xd0 kernel/sched/wait_bit.c:209
 __wait_on_bit+0xb3/0x2e0 kernel/sched/wait_bit.c:49
 out_of_line_wait_on_bit+0x139/0x190 kernel/sched/wait_bit.c:64
 wait_on_bit_io include/linux/wait_bit.h:101 [inline]
 do_get_write_access+0x558/0xd70 fs/jbd2/transaction.c:1096
 jbd2_journal_get_write_access+0x268/0x3d0 fs/jbd2/transaction.c:1245
 __ext4_journal_get_write_access+0x1b6/0x6a0 fs/ext4/ext4_jbd2.c:239
 ext4_reserve_inode_write+0x1f6/0x2e0 fs/ext4/inode.c:5892
 __ext4_mark_inode_dirty+0xac/0x5e0 fs/ext4/inode.c:6066
 ext4_dirty_inode+0xc9/0x110 fs/ext4/inode.c:6103
 __mark_inode_dirty+0x24e/0xc50 fs/fs-writeback.c:2515
 generic_update_time fs/inode.c:2056 [inline]
 inode_update_time fs/inode.c:2069 [inline]
 __file_update_time fs/inode.c:2258 [inline]
 file_update_time+0x1d3/0x210 fs/inode.c:2288
 ext4_page_mkwrite+0x2bf/0x1120 fs/ext4/inode.c:6221
 do_page_mkwrite mm/memory.c:3263 [inline]
 do_shared_fault mm/memory.c:5537 [inline]
 do_fault mm/memory.c:5599 [inline]
 do_pte_missing+0x12c4/0x4440 mm/memory.c:4069
 handle_pte_fault mm/memory.c:5940 [inline]
 __handle_mm_fault mm/memory.c:6083 [inline]
 handle_mm_fault+0x1189/0x1ba0 mm/memory.c:6251
 do_user_addr_fault+0x951/0x1230 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1479 [inline]
 exc_page_fault+0x58/0xc0 arch/x86/mm/fault.c:1534
 asm_exc_page_fault+0x2b/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0033:0x7f2c15e6ba23
RSP: 002b:00007ffca213c1b0 EFLAGS: 00010246
RAX: 000000000003fde8 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000001b34724000 RSI: 0000000000040000 RDI: 00007f2c161e0708
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 00007ffca213c440
 </TASK>
INFO: task syz.3.443:828 blocked for more than 123 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.443       state:D stack:0     pid:828   tgid:828   ppid:384    flags:0x00000004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:6060 [inline]
 __schedule+0x1496/0x20b0 kernel/sched/core.c:7880
 __schedule_loop kernel/sched/core.c:7957 [inline]
 schedule+0xc5/0x240 kernel/sched/core.c:7972
 io_schedule+0x88/0xe0 kernel/sched/core.c:8786
 bit_wait_io+0x17/0xd0 kernel/sched/wait_bit.c:209
 __wait_on_bit+0xb3/0x2e0 kernel/sched/wait_bit.c:49
 out_of_line_wait_on_bit+0x139/0x190 kernel/sched/wait_bit.c:64
 wait_on_bit_io include/linux/wait_bit.h:101 [inline]
 do_get_write_access+0x558/0xd70 fs/jbd2/transaction.c:1096
 jbd2_journal_get_write_access+0x268/0x3d0 fs/jbd2/transaction.c:1245
 __ext4_journal_get_write_access+0x1b6/0x6a0 fs/ext4/ext4_jbd2.c:239
 ext4_reserve_inode_write+0x1f6/0x2e0 fs/ext4/inode.c:5892
 __ext4_mark_inode_dirty+0xac/0x5e0 fs/ext4/inode.c:6066
 ext4_dirty_inode+0xc9/0x110 fs/ext4/inode.c:6103
 __mark_inode_dirty+0x24e/0xc50 fs/fs-writeback.c:2515
 generic_update_time fs/inode.c:2056 [inline]
 inode_update_time fs/inode.c:2069 [inline]
 __file_update_time fs/inode.c:2258 [inline]
 file_update_time+0x1d3/0x210 fs/inode.c:2288
 ext4_page_mkwrite+0x2bf/0x1120 fs/ext4/inode.c:6221
 do_page_mkwrite mm/memory.c:3263 [inline]
 do_shared_fault mm/memory.c:5537 [inline]
 do_fault mm/memory.c:5599 [inline]
 do_pte_missing+0x12c4/0x4440 mm/memory.c:4069
 handle_pte_fault mm/memory.c:5940 [inline]
 __handle_mm_fault mm/memory.c:6083 [inline]
 handle_mm_fault+0x1189/0x1ba0 mm/memory.c:6251
 do_user_addr_fault+0x951/0x1230 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1479 [inline]
 exc_page_fault+0x58/0xc0 arch/x86/mm/fault.c:1534
 asm_exc_page_fault+0x2b/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0033:0x7f46f986ba23
RSP: 002b:00007ffc33dc6e60 EFLAGS: 00010246
RAX: 000000000003fde8 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000001b34b24000 RSI: 0000000000040000 RDI: 00007f46f9be0708
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 00007ffc33dc70f0
 </TASK>
INFO: task syz.4.445:829 blocked for more than 124 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.445       state:D stack:0     pid:829   tgid:829   ppid:380    flags:0x00000004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:6060 [inline]
 __schedule+0x1496/0x20b0 kernel/sched/core.c:7880
 __schedule_loop kernel/sched/core.c:7957 [inline]
 schedule+0xc5/0x240 kernel/sched/core.c:7972
 io_schedule+0x88/0xe0 kernel/sched/core.c:8786
 bit_wait_io+0x17/0xd0 kernel/sched/wait_bit.c:209
 __wait_on_bit+0xb3/0x2e0 kernel/sched/wait_bit.c:49
 out_of_line_wait_on_bit+0x139/0x190 kernel/sched/wait_bit.c:64
 wait_on_bit_io include/linux/wait_bit.h:101 [inline]
 do_get_write_access+0x558/0xd70 fs/jbd2/transaction.c:1096
 jbd2_journal_get_write_access+0x268/0x3d0 fs/jbd2/transaction.c:1245
 __ext4_journal_get_write_access+0x1b6/0x6a0 fs/ext4/ext4_jbd2.c:239
 ext4_reserve_inode_write+0x1f6/0x2e0 fs/ext4/inode.c:5892
 __ext4_mark_inode_dirty+0xac/0x5e0 fs/ext4/inode.c:6066
 ext4_dirty_inode+0xc9/0x110 fs/ext4/inode.c:6103
 __mark_inode_dirty+0x24e/0xc50 fs/fs-writeback.c:2515
 generic_update_time fs/inode.c:2056 [inline]
 inode_update_time fs/inode.c:2069 [inline]
 __file_update_time fs/inode.c:2258 [inline]
 file_update_time+0x1d3/0x210 fs/inode.c:2288
 ext4_page_mkwrite+0x2bf/0x1120 fs/ext4/inode.c:6221
 do_page_mkwrite mm/memory.c:3263 [inline]
 do_shared_fault mm/memory.c:5537 [inline]
 do_fault mm/memory.c:5599 [inline]
 do_pte_missing+0x12c4/0x4440 mm/memory.c:4069
 handle_pte_fault mm/memory.c:5940 [inline]
 __handle_mm_fault mm/memory.c:6083 [inline]
 handle_mm_fault+0x1189/0x1ba0 mm/memory.c:6251
 do_user_addr_fault+0x951/0x1230 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1479 [inline]
 exc_page_fault+0x58/0xc0 arch/x86/mm/fault.c:1534
 asm_exc_page_fault+0x2b/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0033:0x7fbdb126ba23
RSP: 002b:00007ffdaa7ad5d0 EFLAGS: 00010246
RAX: 000000000003fde8 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000001b34624000 RSI: 0000000000040000 RDI: 00007fbdb15e0708
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 00007ffdaa7ad860
 </TASK>
INFO: task syz.5.446:830 blocked for more than 124 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.5.446       state:D stack:0     pid:830   tgid:830   ppid:385    flags:0x00000004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:6060 [inline]
 __schedule+0x1496/0x20b0 kernel/sched/core.c:7880
 __schedule_loop kernel/sched/core.c:7957 [inline]
 schedule+0xc5/0x240 kernel/sched/core.c:7972
 io_schedule+0x88/0xe0 kernel/sched/core.c:8786
 bit_wait_io+0x17/0xd0 kernel/sched/wait_bit.c:209
 __wait_on_bit+0xb3/0x2e0 kernel/sched/wait_bit.c:49
 out_of_line_wait_on_bit+0x139/0x190 kernel/sched/wait_bit.c:64
 wait_on_bit_io include/linux/wait_bit.h:101 [inline]
 do_get_write_access+0x558/0xd70 fs/jbd2/transaction.c:1096
 jbd2_journal_get_write_access+0x268/0x3d0 fs/jbd2/transaction.c:1245
 __ext4_journal_get_write_access+0x1b6/0x6a0 fs/ext4/ext4_jbd2.c:239
 ext4_reserve_inode_write+0x1f6/0x2e0 fs/ext4/inode.c:5892
 __ext4_mark_inode_dirty+0xac/0x5e0 fs/ext4/inode.c:6066
 ext4_dirty_inode+0xc9/0x110 fs/ext4/inode.c:6103
 __mark_inode_dirty+0x24e/0xc50 fs/fs-writeback.c:2515
 generic_update_time fs/inode.c:2056 [inline]
 inode_update_time fs/inode.c:2069 [inline]
 __file_update_time fs/inode.c:2258 [inline]
 file_update_time+0x1d3/0x210 fs/inode.c:2288
 ext4_page_mkwrite+0x2bf/0x1120 fs/ext4/inode.c:6221
 do_page_mkwrite mm/memory.c:3263 [inline]
 do_shared_fault mm/memory.c:5537 [inline]
 do_fault mm/memory.c:5599 [inline]
 do_pte_missing+0x12c4/0x4440 mm/memory.c:4069
 handle_pte_fault mm/memory.c:5940 [inline]
 __handle_mm_fault mm/memory.c:6083 [inline]
 handle_mm_fault+0x1189/0x1ba0 mm/memory.c:6251
 do_user_addr_fault+0x951/0x1230 arch/x86/mm/fault.c:1336
 handle_page_fault arch/x86/mm/fault.c:1479 [inline]
 exc_page_fault+0x58/0xc0 arch/x86/mm/fault.c:1534
 asm_exc_page_fault+0x2b/0x30 arch/x86/include/asm/idtentry.h:623
RIP: 0033:0x7ff38166ba23
RSP: 002b:00007ffc172c34d0 EFLAGS: 00010246
RAX: 000000000003fde8 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000001b34a24000 RSI: 0000000000040000 RDI: 00007ff3819e0708
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 00007ffc172c3760
 </TASK>
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 37 Comm: khungtaskd Not tainted syzkaller #0 9a2c17613351c9eac8e18d74829f474689ac6bc1
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x140/0x1c0 lib/dump_stack.c:120
 dump_stack+0x19/0x20 lib/dump_stack.c:129
 nmi_cpu_backtrace+0x2ba/0x2d0 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x142/0x2c0 lib/nmi_backtrace.c:62
 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:41
 trigger_all_cpu_backtrace include/linux/nmi.h:158 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:267 [inline]
 watchdog+0xe45/0xf90 kernel/hung_task.c:423
 kthread+0x2c7/0x360 kernel/kthread.c:389
 ret_from_fork+0x67/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 360 Comm: kworker/u8:3 Not tainted syzkaller #0 9a2c17613351c9eac8e18d74829f474689ac6bc1
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Workqueue:  0x0 (events_unbound)
RIP: 0010:update_sg_lb_stats kernel/sched/fair.c:-1 [inline]
RIP: 0010:update_sd_lb_stats kernel/sched/fair.c:11346 [inline]
RIP: 0010:sched_balance_find_src_group kernel/sched/fair.c:11606 [inline]
RIP: 0010:sched_balance_rq+0x91f/0x4dd0 kernel/sched/fair.c:12053
Code: fe ff 4c 8b a4 24 e0 00 00 00 4c 89 7c 24 40 49 83 c7 28 ba 58 00 00 00 4c 89 e7 31 f6 e8 99 41 80 00 48 8b 84 24 88 02 00 00 <48> 89 44 24 78 49 8d 44 24 08 48 89 84 24 88 00 00 00 49 8d 44 24
RSP: 0018:ffffc900062d74e0 EFLAGS: 00000046
RAX: ffff888103a76980 RBX: ffff888103a76c20 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffc900062d7840
RBP: ffffc900062d7990 R08: ffffc900062d783f R09: 0000000000000000
R10: ffffc900062d77e8 R11: fffff52000c5af08 R12: ffffc900062d77e8
R13: dffffc0000000000 R14: 00000000fffff023 R15: ffff888103a769a8
FS:  0000000000000000(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055557fd7f4e8 CR3: 0000000102bc0000 CR4: 00000000003526b0
Call Trace:
 <TASK>
 sched_balance_newidle+0x665/0xaa0 kernel/sched/fair.c:13174
 pick_next_task_fair+0x110/0x7a0 kernel/sched/fair.c:9237
 __pick_next_task kernel/sched/core.c:6720 [inline]
 pick_next_task kernel/sched/core.c:7240 [inline]
 __schedule+0x682/0x20b0 kernel/sched/core.c:7778
 __schedule_loop kernel/sched/core.c:7957 [inline]
 schedule+0xc5/0x240 kernel/sched/core.c:7972
 worker_thread+0x10fd/0x13f0 kernel/workqueue.c:3450
 kthread+0x2c7/0x360 kernel/kthread.c:389
 ret_from_fork+0x67/0xa0 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/23 14:29 android16-6.12 e8c85685a629 1e72964b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in __rq_qos_throttle
2026/08/27 07:52 android16-6.12 dc005eca5dc1 a2b77b9e .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in __rq_qos_throttle
* Struck through repros no longer work on HEAD.