bisecting fixing commit since 13d2ce42de8cb98ff952f8de6307f896203854c2 building syzkaller on f213e07ead587b07a84e60c356520bce7277166c testing commit 13d2ce42de8cb98ff952f8de6307f896203854c2 with gcc (GCC) 8.4.1 20210217 kernel signature: 3c70996151e01aa522a286d421b195f967558190f79b741df5ce072deb2a2ed8 run #0: crashed: INFO: task hung in n_tty_read run #1: crashed: INFO: task hung in n_tty_read run #2: crashed: INFO: task hung in n_tty_read run #3: crashed: INFO: task hung in n_tty_read run #4: crashed: INFO: task hung in n_tty_read run #5: crashed: INFO: task hung in n_tty_read run #6: crashed: INFO: task hung in n_tty_read run #7: crashed: INFO: task hung in n_tty_read run #8: crashed: INFO: task hung in n_tty_read run #9: crashed: INFO: task hung in n_tty_read run #10: crashed: INFO: task hung in n_tty_read run #11: crashed: INFO: task hung in n_tty_read run #12: crashed: INFO: task hung in n_tty_read run #13: crashed: INFO: task hung in n_tty_read run #14: crashed: INFO: task hung in n_tty_read run #15: crashed: INFO: task hung in n_tty_read run #16: crashed: INFO: task hung in n_tty_read run #17: crashed: INFO: task hung in console_callback run #18: crashed: INFO: task hung in console_callback run #19: crashed: INFO: task hung in console_callback testing current HEAD eb575cd5d7f60241d016fdd13a9e86d962093c9b testing commit eb575cd5d7f60241d016fdd13a9e86d962093c9b with gcc (GCC) 8.4.1 20210217 kernel signature: a73bb05a45bd8fecc144b1122cab47ab034d3220681e6ba2bd93b8b18e3fb7c6 run #0: crashed: INFO: task hung in n_tty_read run #1: crashed: INFO: task hung in n_tty_read run #2: crashed: INFO: task hung in n_tty_read run #3: crashed: INFO: task hung in n_tty_read run #4: crashed: INFO: task hung in n_tty_read run #5: crashed: INFO: task hung in n_tty_read run #6: crashed: INFO: task hung in n_tty_read run #7: crashed: INFO: task hung in console_callback run #8: crashed: INFO: task hung in console_callback run #9: crashed: INFO: task hung in console_callback revisions tested: 2, total time: 30m8.809790192s (build: 16m20.86698949s, test: 13m26.358653066s) the crash still happens on HEAD commit msg: Linux 4.19.195 crash: INFO: task hung in console_callback Bluetooth: hci0: command 0x0406 tx timeout Bluetooth: hci4: command 0x0406 tx timeout Bluetooth: hci5: command 0x0406 tx timeout Bluetooth: hci1: command 0x0406 tx timeout Bluetooth: hci3: command 0x0406 tx timeout INFO: task kworker/1:3:4715 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. kworker/1:3 D24616 4715 2 0x80000000 Workqueue: events console_callback 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_timeout+0x6f6/0xd20 kernel/time/timer.c:1794 __down_common kernel/locking/semaphore.c:221 [inline] __down+0x180/0x2a0 kernel/locking/semaphore.c:238 down+0x5e/0x80 kernel/locking/semaphore.c:62 console_lock+0x23/0x70 kernel/printk/printk.c:2275 console_callback+0x71/0x370 drivers/tty/vt/vt.c:2832 process_one_work+0x7b9/0x15a0 kernel/workqueue.c:2153 worker_thread+0x85/0xb60 kernel/workqueue.c:2296 kthread+0x347/0x410 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415 INFO: task syz-executor.3:14175 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 D29144 14175 8477 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_timeout+0x6f6/0xd20 kernel/time/timer.c:1794 __down_common kernel/locking/semaphore.c:221 [inline] __down+0x180/0x2a0 kernel/locking/semaphore.c:238 down+0x5e/0x80 kernel/locking/semaphore.c:62 console_lock+0x23/0x70 kernel/printk/printk.c:2275 do_fb_ioctl+0x3fa/0x860 drivers/video/fbdev/core/fbmem.c:1109 fb_ioctl+0xc8/0x140 drivers/video/fbdev/core/fbmem.c:1230 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465a49 Code: 50 10 31 db eb 0a 48 8b 72 08 48 89 d3 48 89 f2 48 85 d2 0f 84 d2 00 00 00 39 4a 30 75 e8 48 8b 4a 08 48 85 db 0f 84 9b 00 00 <00> 83 3d 3f c0 14 01 00 0f 85 7c 00 00 00 48 89 4b 08 48 89 54 24 RSP: 002b:00007fa706c3a188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000055bf40 RCX: 0000000000465a49 RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003 RBP: 00000000004af682 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bf40 R13: 00007ffef8f3ae8f R14: 00007fa706c3a300 R15: 0000000000022000 INFO: task syz-executor.2:14189 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 D29176 14189 8475 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_timeout+0x6f6/0xd20 kernel/time/timer.c:1794 __down_common kernel/locking/semaphore.c:221 [inline] __down+0x180/0x2a0 kernel/locking/semaphore.c:238 down+0x5e/0x80 kernel/locking/semaphore.c:62 console_lock+0x23/0x70 kernel/printk/printk.c:2275 do_fb_ioctl+0x3fa/0x860 drivers/video/fbdev/core/fbmem.c:1109 fb_ioctl+0xc8/0x140 drivers/video/fbdev/core/fbmem.c:1230 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465a49 Code: 50 10 31 db eb 0a 48 8b 72 08 48 89 d3 48 89 f2 48 85 d2 0f 84 d2 00 00 00 39 4a 30 75 e8 48 8b 4a 08 48 85 db 0f 84 9b 00 00 <00> 83 3d 3f c0 14 01 00 0f 85 7c 00 00 00 48 89 4b 08 48 89 54 24 RSP: 002b:00007f84acff8188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000055bf40 RCX: 0000000000465a49 RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003 RBP: 00000000004af682 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bf40 R13: 00007ffecea5fc9f R14: 00007f84acff8300 R15: 0000000000022000 INFO: task syz-executor.2:14199 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 D28792 14199 8475 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_timeout+0x6f6/0xd20 kernel/time/timer.c:1794 __down_common kernel/locking/semaphore.c:221 [inline] __down+0x180/0x2a0 kernel/locking/semaphore.c:238 down+0x5e/0x80 kernel/locking/semaphore.c:62 console_lock+0x23/0x70 kernel/printk/printk.c:2275 do_fb_ioctl+0x3fa/0x860 drivers/video/fbdev/core/fbmem.c:1109 fb_ioctl+0xc8/0x140 drivers/video/fbdev/core/fbmem.c:1230 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465a49 Code: 50 10 31 db eb 0a 48 8b 72 08 48 89 d3 48 89 f2 48 85 d2 0f 84 d2 00 00 00 39 4a 30 75 e8 48 8b 4a 08 48 85 db 0f 84 9b 00 00 <00> 83 3d 3f c0 14 01 00 0f 85 7c 00 00 00 48 89 4b 08 48 89 54 24 RSP: 002b:00007f84acfd7188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000055bfe8 RCX: 0000000000465a49 RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003 RBP: 00000000004af682 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bfe8 R13: 00007ffecea5fc9f R14: 00007f84acfd7300 R15: 0000000000022000 INFO: task syz-executor.1:14186 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 D29096 14186 8483 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_timeout+0x6f6/0xd20 kernel/time/timer.c:1794 __down_common kernel/locking/semaphore.c:221 [inline] __down+0x180/0x2a0 kernel/locking/semaphore.c:238 down+0x5e/0x80 kernel/locking/semaphore.c:62 console_lock+0x23/0x70 kernel/printk/printk.c:2275 do_fb_ioctl+0x3fa/0x860 drivers/video/fbdev/core/fbmem.c:1109 fb_ioctl+0xc8/0x140 drivers/video/fbdev/core/fbmem.c:1230 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465a49 Code: 50 10 31 db eb 0a 48 8b 72 08 48 89 d3 48 89 f2 48 85 d2 0f 84 d2 00 00 00 39 4a 30 75 e8 48 8b 4a 08 48 85 db 0f 84 9b 00 00 <00> 83 3d 3f c0 14 01 00 0f 85 7c 00 00 00 48 89 4b 08 48 89 54 24 RSP: 002b:00007f1c5d3eb188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000055bf40 RCX: 0000000000465a49 RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003 RBP: 00000000004af682 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bf40 R13: 00007fff2adc504f R14: 00007f1c5d3eb300 R15: 0000000000022000 INFO: task syz-executor.1:14201 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 D29176 14201 8483 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_timeout+0x6f6/0xd20 kernel/time/timer.c:1794 __down_common kernel/locking/semaphore.c:221 [inline] __down+0x180/0x2a0 kernel/locking/semaphore.c:238 down+0x5e/0x80 kernel/locking/semaphore.c:62 console_lock+0x23/0x70 kernel/printk/printk.c:2275 do_fb_ioctl+0x3fa/0x860 drivers/video/fbdev/core/fbmem.c:1109 fb_ioctl+0xc8/0x140 drivers/video/fbdev/core/fbmem.c:1230 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465a49 Code: 50 10 31 db eb 0a 48 8b 72 08 48 89 d3 48 89 f2 48 85 d2 0f 84 d2 00 00 00 39 4a 30 75 e8 48 8b 4a 08 48 85 db 0f 84 9b 00 00 <00> 83 3d 3f c0 14 01 00 0f 85 7c 00 00 00 48 89 4b 08 48 89 54 24 RSP: 002b:00007f1c5d3ca188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000055bfe8 RCX: 0000000000465a49 RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003 RBP: 00000000004af682 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bfe8 R13: 00007fff2adc504f R14: 00007f1c5d3ca300 R15: 0000000000022000 INFO: task syz-executor.4:14188 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 D29176 14188 8485 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_timeout+0x6f6/0xd20 kernel/time/timer.c:1794 __down_common kernel/locking/semaphore.c:221 [inline] __down+0x180/0x2a0 kernel/locking/semaphore.c:238 down+0x5e/0x80 kernel/locking/semaphore.c:62 console_lock+0x23/0x70 kernel/printk/printk.c:2275 do_fb_ioctl+0x3fa/0x860 drivers/video/fbdev/core/fbmem.c:1109 fb_ioctl+0xc8/0x140 drivers/video/fbdev/core/fbmem.c:1230 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465a49 Code: 50 10 31 db eb 0a 48 8b 72 08 48 89 d3 48 89 f2 48 85 d2 0f 84 d2 00 00 00 39 4a 30 75 e8 48 8b 4a 08 48 85 db 0f 84 9b 00 00 <00> 83 3d 3f c0 14 01 00 0f 85 7c 00 00 00 48 89 4b 08 48 89 54 24 RSP: 002b:00007f3937f39188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000055bf40 RCX: 0000000000465a49 RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003 RBP: 00000000004af682 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bf40 R13: 00007ffc5de35caf R14: 00007f3937f39300 R15: 0000000000022000 INFO: task syz-executor.4:14198 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 D29176 14198 8485 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_timeout+0x6f6/0xd20 kernel/time/timer.c:1794 __down_common kernel/locking/semaphore.c:221 [inline] __down+0x180/0x2a0 kernel/locking/semaphore.c:238 down+0x5e/0x80 kernel/locking/semaphore.c:62 console_lock+0x23/0x70 kernel/printk/printk.c:2275 do_fb_ioctl+0x3fa/0x860 drivers/video/fbdev/core/fbmem.c:1109 fb_ioctl+0xc8/0x140 drivers/video/fbdev/core/fbmem.c:1230 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465a49 Code: 50 10 31 db eb 0a 48 8b 72 08 48 89 d3 48 89 f2 48 85 d2 0f 84 d2 00 00 00 39 4a 30 75 e8 48 8b 4a 08 48 85 db 0f 84 9b 00 00 <00> 83 3d 3f c0 14 01 00 0f 85 7c 00 00 00 48 89 4b 08 48 89 54 24 RSP: 002b:00007f3937f18188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000055bfe8 RCX: 0000000000465a49 RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003 RBP: 00000000004af682 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bfe8 R13: 00007ffc5de35caf R14: 00007f3937f18300 R15: 0000000000022000 INFO: task syz-executor.0:14190 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 D29096 14190 8481 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_timeout+0x6f6/0xd20 kernel/time/timer.c:1794 __down_common kernel/locking/semaphore.c:221 [inline] __down+0x180/0x2a0 kernel/locking/semaphore.c:238 down+0x5e/0x80 kernel/locking/semaphore.c:62 console_lock+0x23/0x70 kernel/printk/printk.c:2275 do_fb_ioctl+0x3fa/0x860 drivers/video/fbdev/core/fbmem.c:1109 fb_ioctl+0xc8/0x140 drivers/video/fbdev/core/fbmem.c:1230 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465a49 Code: 50 10 31 db eb 0a 48 8b 72 08 48 89 d3 48 89 f2 48 85 d2 0f 84 d2 00 00 00 39 4a 30 75 e8 48 8b 4a 08 48 85 db 0f 84 9b 00 00 <00> 83 3d 3f c0 14 01 00 0f 85 7c 00 00 00 48 89 4b 08 48 89 54 24 RSP: 002b:00007f802fd24188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000055bf40 RCX: 0000000000465a49 RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003 RBP: 00000000004af682 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bf40 R13: 00007ffcfe6df71f R14: 00007f802fd24300 R15: 0000000000022000 INFO: task syz-executor.0:14200 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 D29176 14200 8481 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_timeout+0x6f6/0xd20 kernel/time/timer.c:1794 __down_common kernel/locking/semaphore.c:221 [inline] __down+0x180/0x2a0 kernel/locking/semaphore.c:238 down+0x5e/0x80 kernel/locking/semaphore.c:62 console_lock+0x23/0x70 kernel/printk/printk.c:2275 do_fb_ioctl+0x3fa/0x860 drivers/video/fbdev/core/fbmem.c:1109 fb_ioctl+0xc8/0x140 drivers/video/fbdev/core/fbmem.c:1230 vfs_ioctl fs/ioctl.c:46 [inline] file_ioctl fs/ioctl.c:501 [inline] do_vfs_ioctl+0x196/0x10c0 fs/ioctl.c:688 ksys_ioctl+0x62/0x90 fs/ioctl.c:705 __do_sys_ioctl fs/ioctl.c:712 [inline] __se_sys_ioctl fs/ioctl.c:710 [inline] __x64_sys_ioctl+0x6e/0xb0 fs/ioctl.c:710 do_syscall_64+0xd0/0x4e0 arch/x86/entry/common.c:293 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x465a49 Code: 50 10 31 db eb 0a 48 8b 72 08 48 89 d3 48 89 f2 48 85 d2 0f 84 d2 00 00 00 39 4a 30 75 e8 48 8b 4a 08 48 85 db 0f 84 9b 00 00 <00> 83 3d 3f c0 14 01 00 0f 85 7c 00 00 00 48 89 4b 08 48 89 54 24 RSP: 002b:00007f802fd03188 EFLAGS: 00000246 ORIG_RAX: 0000000000000010 RAX: ffffffffffffffda RBX: 000000000055bfe8 RCX: 0000000000465a49 RDX: 0000000020000000 RSI: 0000000000004601 RDI: 0000000000000003 RBP: 00000000004af682 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 000000000055bfe8 R13: 00007ffcfe6df71f R14: 00007f802fd03300 R15: 0000000000022000 Showing all locks held in the system: 1 lock held by khungtaskd/1569: #0: 00000000daa69994 (rcu_read_lock){....}, at: debug_show_all_locks+0x5b/0x27a kernel/locking/lockdep.c:4443 2 locks held by kworker/1:3/4715: #0: 00000000631e9838 ((wq_completion)"events"){+.+.}, at: process_one_work+0x6e8/0x15a0 kernel/workqueue.c:2124 #1: 00000000aaf86c55 (console_work){+.+.}, at: process_one_work+0x71b/0x15a0 kernel/workqueue.c:2128 1 lock held by in:imklog/7818: #0: 00000000c8567422 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xa7/0xd0 fs/file.c:767 2 locks held by agetty/8044: #0: 000000002140edce (&tty->ldisc_sem){++++}, at: ldsem_down_read+0x2d/0x40 drivers/tty/tty_ldsem.c:362 #1: 000000007f063c4b (&ldata->atomic_read_lock){+.+.}, at: n_tty_read+0x1ee/0x1910 drivers/tty/n_tty.c:2154 7 locks held by kworker/u4:5/9271: ============================================= NMI backtrace for cpu 1 CPU: 1 PID: 1569 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 CPU: 0 PID: 9271 Comm: kworker/u4:5 Not tainted 4.19.195-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Workqueue: events_unbound flush_to_ldisc RIP: 0010:vga16fb_fillrect+0x881/0x19b0 drivers/video/fbdev/vga16fb.c:924 Code: 8d 70 ff 85 c0 0f 84 30 fd ff ff 4c 63 7d c8 41 8d 7c 24 ff 31 d2 48 83 c7 01 49 8d 04 3e 45 85 e4 0f 84 0b 07 00 00 41 88 16 <49> 83 c6 01 49 39 c6 75 f4 4e 8d 34 38 83 ee 01 83 fe ff 75 db e9 RSP: 0018:ffff8880913ff418 EFLAGS: 00000283 RAX: ffff8880000a0050 RBX: 0000000000000000 RCX: 00000000ffffffb0 RDX: 0000000000000000 RSI: 0000000043a201d9 RDI: 0000000000000050 RBP: ffff8880913ff490 R08: ffff8880913ff4dc R09: 0000000000000000 R10: 1ffff110277c4eb9 R11: 0000000000000000 R12: 0000000000000050 R13: 1ffffffff132248a R14: ffff8880000a0020 R15: ffffffffffffffb0 FS: 0000000000000000(0000) GS:ffff8880ba200000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fa95ba81000 CR3: 00000000ab706000 CR4: 00000000001406f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: bit_clear+0x314/0x630 drivers/video/fbdev/core/bitblit.c:74 fbcon_clear+0x475/0x700 drivers/video/fbdev/core/fbcon.c:1258 fbcon_scroll+0x618/0x3530 drivers/video/fbdev/core/fbcon.c:1759 con_scroll+0x467/0x700 drivers/tty/vt/vt.c:637 lf+0x23b/0x2a0 drivers/tty/vt/vt.c:1492 do_con_write.part.13+0x10f0/0x1aa0 drivers/tty/vt/vt.c:2769 do_con_write drivers/tty/vt/vt.c:3157 [inline] con_put_char+0xaf/0xc0 drivers/tty/vt/vt.c:3156 tty_put_char+0xac/0x130 drivers/tty/tty_io.c:2892 do_output_char+0x1c9/0x700 drivers/tty/n_tty.c:486 __process_echoes+0x287/0x790 drivers/tty/n_tty.c:737 commit_echoes+0x10e/0x160 drivers/tty/n_tty.c:792 n_tty_receive_char_fast drivers/tty/n_tty.c:1447 [inline] n_tty_receive_buf_fast drivers/tty/n_tty.c:1607 [inline] __receive_buf drivers/tty/n_tty.c:1642 [inline] n_tty_receive_buf_common+0x1363/0x2db0 drivers/tty/n_tty.c:1740 n_tty_receive_buf2+0xf/0x20 drivers/tty/n_tty.c:1775 tty_ldisc_receive_buf+0x86/0x1b0 drivers/tty/tty_buffer.c:456 tty_port_default_receive_buf+0x5f/0x90 drivers/tty/tty_port.c:38 receive_buf drivers/tty/tty_buffer.c:476 [inline] flush_to_ldisc+0x1aa/0x3a0 drivers/tty/tty_buffer.c:528 process_one_work+0x7b9/0x15a0 kernel/workqueue.c:2153 worker_thread+0x85/0xb60 kernel/workqueue.c:2296 kthread+0x347/0x410 kernel/kthread.c:259 ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415