Server rebooted with many adclient processes in uninterruptable sleep

Issue

• We run adclient on a server and it became unresponsive.
• Server was rebooted due to hung_task_panic.
• The following call traces appear in logs:

INFO: task adclient:1670 blocked for more than 120 seconds.
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
adclient      D 0000000000000004     0  1670      1 0x00000080
 ffff88083223dc98 0000000000000082 ffff88083487ec80 000492d02e736040
 ffff88083223dc68 ffffffff810aa4e0 0000000000000246 0000000000000286
 ffff88082e7365f8 ffff88083223dfd8 000000000000fb88 ffff88082e7365f8
Call Trace:
 [<ffffffff810aa4e0>] ? exit_robust_list+0x90/0x160
 [<ffffffff81072f95>] exit_mm+0x95/0x180
 [<ffffffff810733df>] do_exit+0x15f/0x870
 [<ffffffff81073b48>] do_group_exit+0x58/0xd0
 [<ffffffff81088e36>] get_signal_to_deliver+0x1f6/0x460
 [<ffffffff8100a265>] do_signal+0x75/0x800
 [<ffffffff81435f05>] ? sys_sendto+0x185/0x190
 [<ffffffff8100988e>] ? __switch_to+0x26e/0x320
 [<ffffffff8100bb8e>] ? apic_timer_interrupt+0xe/0x20
 [<ffffffff810acd7b>] ? sys_futex+0x7b/0x170
 [<ffffffff8100aa80>] do_notify_resume+0x90/0xc0
 [<ffffffff8100b341>] int_signal+0x12/0x17