Date: 2018oct15 OS: Linux Q. Linux: stack trace of any running process A.

cat /proc/$PID/stack

For eample of an idle BOINC

[<0>] poll_schedule_timeout+0x41/0x70 [<0>] do_select+0x526/0x780 [<0>] core_sys_select+0x20e/0x2f0 [<0>] kern_select+0xb5/0x110 [<0>] __x64_sys_select+0x20/0x30 [<0>] do_syscall_64+0x5b/0x160 [<0>] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [<0>] 0xffffffffffffffff