When we get a hung task it can often be valuable to see _all_ the held locks on the system (in case we are being blocked on trying to acquire one), e.g. with this patch we can immediately see where the problem is below: INFO: task trinity-c3:14933 blocked for more than 120 seconds. Not tainted 4.8.0-rc1+ #135 "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. trinity-c3 D ffff88010c16fc88 0 14933 1 0x00080004 ffff88010c16fc88 000000003b9aca00 0000000000000000 0000000000000296 00000000776cdf88 ffff88011a520ae0 ffff88011a520b08 ffff88011a520198 ffffffff867d7f00 ffff88011942c080 ffff880116841580 ffff88010c168000 Call Trace: [<ffffffff845e9d37>] schedule+0x77/0x230 [<ffffffff833cb8b9>] __lock_sock+0x129/0x250 [<ffffffff833cb790>] ? __sk_destruct+0x450/0x450 [<ffffffff81408ac0>] ? wake_bit_function+0x2e0/0x2e0 [<ffffffff833d832b>] lock_sock_nested+0xeb/0x120 [<ffffffff83bad815>] irda_setsockopt+0x65/0xb40 [<ffffffff833c6c09>] SyS_setsockopt+0x139/0x230 [<ffffffff833c6ad0>] ? SyS_recv+0x20/0x20 [<ffffffff81004660>] ? trace_event_raw_event_sys_enter+0xb90/0xb90 [<ffffffff823c7023>] ? __this_cpu_preempt_check+0x13/0x20 [<ffffffff8162ee60>] ? __context_tracking_exit.part.3+0x30/0x1b0 [<ffffffff833c6ad0>] ? SyS_recv+0x20/0x20 [<ffffffff81007bd3>] do_syscall_64+0x1b3/0x4b0 [<ffffffff845f84aa>] entry_SYSCALL64_slow_path+0x25/0x25 Showing all locks held in the system: 2 locks held by khungtaskd/563: #0: (rcu_read_lock){......}, at: [<ffffffff81534ce6>] watchdog+0x106/0x910 #1: (tasklist_lock){......}, at: [<ffffffff8141b3c4>] debug_show_all_locks+0x74/0x360 1 lock held by trinity-c0/19280: #0: (sk_lock-AF_IRDA){......}, at: [<ffffffff83bab7c6>] irda_accept+0x176/0x10f0 1 lock held by trinity-c0/12865: #0: (sk_lock-AF_IRDA){......}, at: [<ffffffff83bab7c6>] irda_accept+0x176/0x10f0
Showing the changes to kernel/hung_task.c (1 of 1 file). Show all
Unified · Split
| @@ -117,7 +117,7 @@ static void check_hung_task(struct task_struct *t, unsigned long timeout) · 116 unmodified lines | ||
| 117 | 117 | pr_err("\"echo 0 > /proc/sys/kernel/hung_task_timeout_secs\"" |
| 118 | 118 | " disables this message.\n"); |
| 119 | 119 | sched_show_task(t); |
| 120 | − debug_show_held_locks(t); | |
| 120 | + debug_show_all_locks(); | |
| 121 | 121 | |
| 122 | 122 | touch_nmi_watchdog(); |
| 123 | 123 | |