bisecting fixing commit since 811218eceeaa7618652e1b8d11caeff67ab42072 building syzkaller on a52ee10ae11c1342cfca60cf3957619bcf92bd1a testing commit 811218eceeaa7618652e1b8d11caeff67ab42072 with gcc (GCC) 8.4.1 20210217 kernel signature: 44ff2e098eb37a46a4162839c884313bd4abc05d25b38a8351e2f8d98bade116 all runs: crashed: INFO: task hung in acct testing current HEAD eb575cd5d7f60241d016fdd13a9e86d962093c9b testing commit eb575cd5d7f60241d016fdd13a9e86d962093c9b with gcc (GCC) 8.4.1 20210217 kernel signature: edfafcfde90b0b1fdc73cf17d844a03371434442dbf33a498b3bef4108ec2ae1 all runs: crashed: INFO: task hung in acct revisions tested: 2, total time: 34m23.423187989s (build: 14m38.799267075s, test: 19m19.728582732s) the crash still happens on HEAD commit msg: Linux 4.19.195 crash: INFO: task hung in acct Bluetooth: hci1: command 0x0406 tx timeout Bluetooth: hci5: command 0x0406 tx timeout Bluetooth: hci4: command 0x0406 tx timeout Bluetooth: hci0: command 0x0406 tx timeout Bluetooth: hci3: command 0x0406 tx timeout INFO: task syz-executor.2:11406 blocked for more than 140 seconds. Not tainted 4.19.195-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.2 D28664 11406 10473 0x00000004 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3619 __mutex_lock_common kernel/locking/mutex.c:1015 [inline] __mutex_lock+0x4ba/0x1190 kernel/locking/mutex.c:1083 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1098 __do_sys_acct kernel/acct.c:285 [inline] __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 __x64_sys_acct+0x2c/0x40 kernel/acct.c:273 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465b09 Code: Bad RIP value. RSP: 002b:00007f3a353a2188 EFLAGS: 00000246 ORIG_RAX: 00000000000000a3 RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465b09 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200001c0 RBP: 00000000004b069f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007ffc1d6e583f R14: 00007f3a353a2300 R15: 0000000000022000 INFO: task syz-executor.4:11414 blocked for more than 140 seconds. Not tainted 4.19.195-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D28664 11414 10482 0x00000000 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3619 __mutex_lock_common kernel/locking/mutex.c:1015 [inline] __mutex_lock+0x4ba/0x1190 kernel/locking/mutex.c:1083 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1098 __do_sys_acct kernel/acct.c:285 [inline] __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 __x64_sys_acct+0x2c/0x40 kernel/acct.c:273 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465b09 Code: Bad RIP value. RSP: 002b:00007f362f56d188 EFLAGS: 00000246 ORIG_RAX: 00000000000000a3 RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465b09 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200001c0 RBP: 00000000004b069f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007fff1f9489ff R14: 00007f362f56d300 R15: 0000000000022000 INFO: task syz-executor.4:11424 blocked for more than 140 seconds. Not tainted 4.19.195-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D29784 11424 10482 0x00000000 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3619 __mutex_lock_common kernel/locking/mutex.c:1015 [inline] __mutex_lock+0x4ba/0x1190 kernel/locking/mutex.c:1083 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1098 __do_sys_acct kernel/acct.c:285 [inline] __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 __x64_sys_acct+0x2c/0x40 kernel/acct.c:273 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465b09 Code: Bad RIP value. RSP: 002b:00007f362f56d188 EFLAGS: 00000246 ORIG_RAX: 00000000000000a3 RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465b09 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200001c0 RBP: 00000000004b069f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007fff1f9489ff R14: 00007f362f56d300 R15: 0000000000022000 INFO: task syz-executor.4:11426 blocked for more than 140 seconds. Not tainted 4.19.195-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D29448 11426 10482 0x00000000 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3619 __mutex_lock_common kernel/locking/mutex.c:1015 [inline] __mutex_lock+0x4ba/0x1190 kernel/locking/mutex.c:1083 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1098 __do_sys_acct kernel/acct.c:285 [inline] __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 __x64_sys_acct+0x2c/0x40 kernel/acct.c:273 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465b09 Code: Bad RIP value. RSP: 002b:00007f362f56d188 EFLAGS: 00000246 ORIG_RAX: 00000000000000a3 RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465b09 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200001c0 RBP: 00000000004b069f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007fff1f9489ff R14: 00007f362f56d300 R15: 0000000000022000 INFO: task syz-executor.4:11433 blocked for more than 140 seconds. Not tainted 4.19.195-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.4 D29784 11433 10482 0x00000000 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3619 __mutex_lock_common kernel/locking/mutex.c:1015 [inline] __mutex_lock+0x4ba/0x1190 kernel/locking/mutex.c:1083 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1098 __do_sys_acct kernel/acct.c:285 [inline] __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 __x64_sys_acct+0x2c/0x40 kernel/acct.c:273 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465b09 Code: Bad RIP value. RSP: 002b:00007f362f56d188 EFLAGS: 00000246 ORIG_RAX: 00000000000000a3 RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465b09 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200001c0 RBP: 00000000004b069f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007fff1f9489ff R14: 00007f362f56d300 R15: 0000000000022000 INFO: task syz-executor.0:12432 blocked for more than 140 seconds. Not tainted 4.19.195-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D29448 12432 11410 0x00000000 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3619 __mutex_lock_common kernel/locking/mutex.c:1015 [inline] __mutex_lock+0x4ba/0x1190 kernel/locking/mutex.c:1083 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1098 __do_sys_acct kernel/acct.c:285 [inline] __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 __x64_sys_acct+0x2c/0x40 kernel/acct.c:273 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465b09 Code: 00 e9 30 ff ff ff 83 f9 77 75 26 48 83 b8 d8 00 00 00 00 7c e2 83 f9 72 75 10 80 78 19 00 74 0a b9 03 00 00 00 e9 0c ff ff ff <31> c9 e9 05 ff ff ff 83 f9 72 eb e2 e8 c6 35 00 00 e9 c1 fe ff ff RSP: 002b:00007f28a7921188 EFLAGS: 00000246 ORIG_RAX: 00000000000000a3 RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465b09 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200001c0 RBP: 00000000004b069f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007ffe081d682f R14: 00007f28a7921300 R15: 0000000000022000 INFO: task syz-executor.0:12443 blocked for more than 140 seconds. Not tainted 4.19.195-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.0 D28664 12443 11410 0x00000000 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3619 __mutex_lock_common kernel/locking/mutex.c:1015 [inline] __mutex_lock+0x4ba/0x1190 kernel/locking/mutex.c:1083 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1098 __do_sys_acct kernel/acct.c:285 [inline] __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 __x64_sys_acct+0x2c/0x40 kernel/acct.c:273 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465b09 Code: 00 e9 30 ff ff ff 83 f9 77 75 26 48 83 b8 d8 00 00 00 00 7c e2 83 f9 72 75 10 80 78 19 00 74 0a b9 03 00 00 00 e9 0c ff ff ff <31> c9 e9 05 ff ff ff 83 f9 72 eb e2 e8 c6 35 00 00 e9 c1 fe ff ff RSP: 002b:00007f28a7921188 EFLAGS: 00000246 ORIG_RAX: 00000000000000a3 RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465b09 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200001c0 RBP: 00000000004b069f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007ffe081d682f R14: 00007f28a7921300 R15: 0000000000022000 INFO: task syz-executor.5:12466 blocked for more than 140 seconds. Not tainted 4.19.195-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.5 D29784 12466 11427 0x00000000 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3619 __mutex_lock_common kernel/locking/mutex.c:1015 [inline] __mutex_lock+0x4ba/0x1190 kernel/locking/mutex.c:1083 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1098 __do_sys_acct kernel/acct.c:285 [inline] __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 __x64_sys_acct+0x2c/0x40 kernel/acct.c:273 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465b09 Code: 00 e9 30 ff ff ff 83 f9 77 75 26 48 83 b8 d8 00 00 00 00 7c e2 83 f9 72 75 10 80 78 19 00 74 0a b9 03 00 00 00 e9 0c ff ff ff <31> c9 e9 05 ff ff ff 83 f9 72 eb e2 e8 c6 35 00 00 e9 c1 fe ff ff RSP: 002b:00007fb5539be188 EFLAGS: 00000246 ORIG_RAX: 00000000000000a3 RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465b09 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200001c0 RBP: 00000000004b069f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007ffe290ef5df R14: 00007fb5539be300 R15: 0000000000022000 INFO: task syz-executor.3:12488 blocked for more than 140 seconds. Not tainted 4.19.195-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.3 D28664 12488 11428 0x00000004 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3619 __mutex_lock_common kernel/locking/mutex.c:1015 [inline] __mutex_lock+0x4ba/0x1190 kernel/locking/mutex.c:1083 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1098 __do_sys_acct kernel/acct.c:285 [inline] __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 __x64_sys_acct+0x2c/0x40 kernel/acct.c:273 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465b09 Code: 00 e9 30 ff ff ff 83 f9 77 75 26 48 83 b8 d8 00 00 00 00 7c e2 83 f9 72 75 10 80 78 19 00 74 0a b9 03 00 00 00 e9 0c ff ff ff <31> c9 e9 05 ff ff ff 83 f9 72 eb e2 e8 c6 35 00 00 e9 c1 fe ff ff RSP: 002b:00007fc19b4a1188 EFLAGS: 00000246 ORIG_RAX: 00000000000000a3 RAX: ffffffffffffffda RBX: 000000000056c008 RCX: 0000000000465b09 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200001c0 RBP: 00000000004b069f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c008 R13: 00007ffd5bbe301f R14: 00007fc19b4a1300 R15: 0000000000022000 INFO: task syz-executor.1:12485 blocked for more than 140 seconds. Not tainted 4.19.195-syzkaller #0 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. syz-executor.1 D29448 12485 11423 0x00000000 Call Trace: context_switch kernel/sched/core.c:2828 [inline] __schedule+0x80c/0x1f70 kernel/sched/core.c:3517 schedule+0x7f/0x1b0 kernel/sched/core.c:3561 schedule_preempt_disabled+0x13/0x20 kernel/sched/core.c:3619 __mutex_lock_common kernel/locking/mutex.c:1015 [inline] __mutex_lock+0x4ba/0x1190 kernel/locking/mutex.c:1083 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:1098 __do_sys_acct kernel/acct.c:285 [inline] __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 __x64_sys_acct+0x2c/0x40 kernel/acct.c:273 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465b09 Code: 00 e9 30 ff ff ff 83 f9 77 75 26 48 83 b8 d8 00 00 00 00 7c e2 83 f9 72 75 10 80 78 19 00 74 0a b9 03 00 00 00 e9 0c ff ff ff <31> c9 e9 05 ff ff ff 83 f9 72 eb e2 e8 c6 35 00 00 e9 c1 fe ff ff RSP: 002b:00007f5285f66188 EFLAGS: 00000246 ORIG_RAX: 00000000000000a3 RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465b09 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000200001c0 RBP: 00000000004b069f R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60 R13: 00007ffc47ae34cf R14: 00007f5285f66300 R15: 0000000000022000 Showing all locks held in the system: 1 lock held by khungtaskd/1570: #0: 0000000051e5c1f4 (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4443 1 lock held by in:imklog/7741: #0: 000000000153ed4b (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:767 1 lock held by syz-executor.2/11406: #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __do_sys_acct kernel/acct.c:285 [inline] #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 1 lock held by syz-executor.4/11404: #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __do_sys_acct kernel/acct.c:285 [inline] #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 1 lock held by syz-executor.4/11414: #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __do_sys_acct kernel/acct.c:285 [inline] #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 1 lock held by syz-executor.4/11424: #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __do_sys_acct kernel/acct.c:285 [inline] #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 1 lock held by syz-executor.4/11426: #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __do_sys_acct kernel/acct.c:285 [inline] #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 1 lock held by syz-executor.4/11433: #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __do_sys_acct kernel/acct.c:285 [inline] #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 1 lock held by syz-executor.0/12432: #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __do_sys_acct kernel/acct.c:285 [inline] #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 1 lock held by syz-executor.0/12443: #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __do_sys_acct kernel/acct.c:285 [inline] #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 1 lock held by syz-executor.5/12466: #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __do_sys_acct kernel/acct.c:285 [inline] #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 1 lock held by syz-executor.3/12488: #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __do_sys_acct kernel/acct.c:285 [inline] #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 1 lock held by syz-executor.1/12485: #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __do_sys_acct kernel/acct.c:285 [inline] #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 1 lock held by syz-executor.3/12487: #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __do_sys_acct kernel/acct.c:285 [inline] #0: 0000000007e72abe (acct_on_mutex){+.+.}, at: __se_sys_acct+0x65/0x7d0 kernel/acct.c:273 ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1570 Comm: khungtaskd Not tainted 4.19.195-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x17c/0x226 lib/dump_stack.c:118 nmi_cpu_backtrace.cold.0+0x3c/0x78 lib/nmi_backtrace.c:101 nmi_trigger_cpumask_backtrace+0xf6/0x120 lib/nmi_backtrace.c:62 arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38 trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline] check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline] watchdog+0x5c3/0xb40 kernel/hung_task.c:287 kthread+0x347/0x410 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 Sending NMI from CPU 1 to CPUs 0: NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0x12/0x20 arch/x86/include/asm/irqflags.h:60