INFO: task hung in pipe_write

Status: auto-obsoleted due to no activity on 2026/02/21 10:27
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+3c4aba8bf87808220033@syzkaller.appspotmail.com
First crash: 326d, last: 271d
▶ ▼ Bug presence (2)
Date Name Commit Repro Result
2025/09/09 lts (merge base) d90ecb2b1308 C [report] INFO: task hung in pipe_write
2025/09/09 upstream (ToT) f777d1112ee5 C [report] INFO: task hung in anon_pipe_write
▶ ▼ Similar bugs (15)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in pipe_write (3) fs 1 1 2377d 2377d 0/29 auto-closed as invalid on 2020/04/25 05:37
android-44 INFO: task hung in pipe_write 1 1 2792d 2664d 0/2 auto-closed as invalid on 2019/06/05 06:19
upstream INFO: task hung in pipe_write (5) fs 1 4 620d 660d 0/29 auto-obsoleted due to no activity on 2025/02/15 05:49
upstream INFO: task hung in rtnetlink_rcv_msg net 1 syz, C inconclusive inconclusive 1970 751d 2714d 26/29 fixed on 2024/07/09 19:14
upstream INFO: task hung in pipe_write (2) ext4 1 syz, C done 6 2506d 2505d 0/29 closed as invalid on 2019/09/28 02:25
upstream INFO: task hung in pipe_write fs 1 8 2736d 2850d 0/29 auto-closed as invalid on 2019/07/30 21:09
linux-4.14 INFO: task hung in pipe_write 1 syz, C 1 1258d 1375d 0/1 upstream: reported C repro on 2022/10/24 05:45
android-44 INFO: task hung in pipe_write (2) 1 1 2432d 2432d 0/2 auto-closed as invalid on 2020/03/31 01:26
android-49 INFO: task hung in pipe_write 1 syz, C 3 2458d 2664d 0/3 public: reported C repro on 2019/04/14 08:51
linux-4.19 INFO: task hung in pipe_write 1 syz, C error 13 1345d 2244d 0/1 upstream: reported C repro on 2020/06/07 01:40
upstream INFO: task hung in pipe_write (6) kernfs netfs 1 syz, C done done 10 304d 527d 0/29 auto-obsoleted due to no activity on 2026/01/07 06:32
upstream INFO: task hung in pipe_write (4) fs 1 syz error 7 1644d 2191d 0/29 auto-obsoleted due to no activity on 2022/10/22 17:00
android-414 INFO: task hung in pipe_write 1 1 2480d 2480d 0/1 auto-closed as invalid on 2020/02/11 22:17
upstream INFO: task can't die in pipe_write (2) fs 1 1 1743d 1739d 0/29 auto-closed as invalid on 2021/12/19 10:46
upstream INFO: task can't die in pipe_write fs 1 1 1817d 1791d 0/29 auto-closed as invalid on 2021/10/06 11:40
▶ ▼ Last patch testing requests (3)
Created Duration User Patch Repo Result
2026/02/21 10:04 15m retest repro android16-6.12 OK log
2025/12/13 09:12 4m retest repro android16-6.12 error
2025/10/04 06:16 17m retest repro android16-6.12 report log

Sample crash report:
INFO: task kworker/1:4:1174 blocked for more than 122 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kworker/1:4     state:D stack:0     pid:1174  tgid:1174  ppid:2      flags:0x00004000
Workqueue: events p9_write_work
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5945 [inline]
 __schedule+0x1322/0x1df0 kernel/sched/core.c:7791
 __schedule_loop kernel/sched/core.c:7872 [inline]
 schedule+0xc6/0x240 kernel/sched/core.c:7887
 schedule_preempt_disabled+0x14/0x30 kernel/sched/core.c:7944
 __mutex_lock_common kernel/locking/mutex.c:707 [inline]
 __mutex_lock+0x81e/0x1b50 kernel/locking/mutex.c:803
 __mutex_lock_slowpath+0xe/0x20 kernel/locking/mutex.c:1134
 mutex_lock+0x102/0x1c0 kernel/locking/mutex.c:285
 pipe_write+0x134/0x18a0 fs/pipe.c:455
 __kernel_write_iter+0x41a/0x8e0 fs/read_write.c:617
 __kernel_write fs/read_write.c:637 [inline]
 kernel_write+0x2e6/0x6b0 fs/read_write.c:658
 p9_fd_write net/9p/trans_fd.c:433 [inline]
 p9_write_work+0x551/0xd30 net/9p/trans_fd.c:484
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x7d2/0x1020 kernel/workqueue.c:3319
 worker_thread+0xc58/0x1250 kernel/workqueue.c:3400
 kthread+0x2ca/0x370 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.2.7020:21692 blocked for more than 123 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.2.7020      state:D stack:0     pid:21692 tgid:21688 ppid:20908  flags:0x00000004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5945 [inline]
 __schedule+0x1322/0x1df0 kernel/sched/core.c:7791
 __schedule_loop kernel/sched/core.c:7872 [inline]
 schedule+0xc6/0x240 kernel/sched/core.c:7887
 schedule_preempt_disabled+0x14/0x30 kernel/sched/core.c:7944
 rwsem_down_write_slowpath+0x9e8/0x1b90 kernel/locking/rwsem.c:1239
 __down_write_common kernel/locking/rwsem.c:1383 [inline]
 __down_write kernel/locking/rwsem.c:1392 [inline]
 down_write+0x152/0x2a0 kernel/locking/rwsem.c:1659
 inode_lock include/linux/fs.h:817 [inline]
 do_lock_mount+0x201/0x520 fs/namespace.c:2618
 lock_mount fs/namespace.c:2663 [inline]
 do_new_mount_fc fs/namespace.c:3472 [inline]
 do_new_mount+0x384/0xb40 fs/namespace.c:3539
 path_mount+0x688/0x1050 fs/namespace.c:3864
 do_mount fs/namespace.c:3877 [inline]
 __do_sys_mount fs/namespace.c:4087 [inline]
 __se_sys_mount+0x2bd/0x480 fs/namespace.c:4064
 __x64_sys_mount+0xc3/0xf0 fs/namespace.c:4064
 x64_sys_call+0x2021/0x2ee0 arch/x86/include/generated/asm/syscalls_64.h:166
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x58/0xf0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x76/0x7e
RIP: 0033:0x7fcb5698efc9
RSP: 002b:00007fcb577de038 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fcb56be6090 RCX: 00007fcb5698efc9
RDX: 0000200000002100 RSI: 0000200000000000 RDI: 0000000000000000
RBP: 00007fcb56a11f91 R08: 0000200000002140 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fcb56be6128 R14: 00007fcb56be6090 R15: 00007fff82c88ec8
 </TASK>
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 37 Comm: khungtaskd Not tainted syzkaller #0 0b5ffdee5fcd2f7749818d1ff954e9c21353764e
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Call Trace:
 <TASK>
 __dump_stack+0x21/0x30 lib/dump_stack.c:94
 dump_stack_lvl+0x10c/0x190 lib/dump_stack.c:120
 dump_stack+0x19/0x20 lib/dump_stack.c:129
 nmi_cpu_backtrace+0x2bf/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+0xd8f/0xed0 kernel/hung_task.c:423
 kthread+0x2ca/0x370 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: 0 Comm: swapper/1 Not tainted syzkaller #0 0b5ffdee5fcd2f7749818d1ff954e9c21353764e
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
RIP: 0010:pv_native_safe_halt+0x17/0x20 arch/x86/kernel/paravirt.c:106
Code: cc cc cc b8 ff b3 28 6c 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d c3 e2 39 00 f3 0f 1e fa 55 48 89 e5 fb f4 <5d> e9 d3 54 02 00 cc cc cc b8 00 00 00 00 90 90 90 90 90 90 90 90
RSP: 0018:ffffc900001a7e00 EFLAGS: 000002c2
RAX: ffff8881f6f00000 RBX: ffff88810366b900 RCX: ffffffff858d70be
RDX: 0000000000000001 RSI: 0000000000000004 RDI: 00000000008c6bfc
RBP: ffffc900001a7e00 R08: ffff8881f6f39733 R09: 1ffff1103ede72e6
R10: dffffc0000000000 R11: ffffed103ede72e7 R12: 1ffff110206cd720
R13: 0000000000000001 R14: 0000000000000000 R15: ffffffff87cb2128
FS:  0000000000000000(0000) GS:ffff8881f6f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 0000000129390000 CR4: 00000000003526b0
DR0: ffffffffffffffff DR1: 00000000000001f8 DR2: 0000000000000083
DR3: ffffffffefffff15 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 arch_safe_halt arch/x86/include/asm/paravirt.h:112 [inline]
 default_idle+0x17/0x30 arch/x86/kernel/process.c:754
 arch_cpu_idle+0xd/0x20 arch/x86/kernel/process.c:791
 default_idle_call+0x3f/0x80 kernel/sched/idle.c:117
 cpuidle_idle_call kernel/sched/idle.c:185 [inline]
 do_idle+0x1a0/0x470 kernel/sched/idle.c:326
 cpu_startup_entry+0x48/0x70 kernel/sched/idle.c:424
 start_secondary+0x12e/0x140 arch/x86/kernel/smpboot.c:314
 common_startup_64+0x13b/0x157
 </TASK>

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/11/01 04:08 android16-6.12 0d6730ee6542 2c50b6a9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in pipe_write
2025/10/26 08:16 android16-6.12 0d6730ee6542 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in pipe_write
2025/10/23 05:07 android16-6.12 0d6730ee6542 c0460fcd .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in pipe_write
2025/09/20 02:51 android16-6.12 8419b8c58fd1 67c37560 .config console log report info [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in pipe_write
2025/09/06 22:57 android16-6.12 ad3375325ca2 d291dd2d .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-android-6-12-rust INFO: task hung in pipe_write
* Struck through repros no longer work on HEAD.