Arch Linux

yuvadm

Member

From: Tel Aviv-Jaffa, Israel

Registered: 2012-08-08

Posts: 103

Website

kworker consuming 100% cpu with empty stack

Recently I've been seeing weird behavior where a kworker process seems to be stuck consuming 100% of a single CPU core without any reason. This is fine if it was temporary, but when it happens it just seems to run forever (even had one running all night without noticing) and the weird thing is this:

# cat /proc/<offending_pid>/stack
[<ffffffffffffffff>] 0xffffffffffffffff

Nothing helps this problem unless I reboot. Is this a kernel bug of some sort? How can I figure out what's causing this?

mich41

Member

Registered: 2012-06-22

Posts: 796

Re: kworker consuming 100% cpu with empty stack

You'll get the same output for every kernel thread.

Maybe perf would be able to tell what's going there.

yuvadm

Member

From: Tel Aviv-Jaffa, Israel

Registered: 2012-08-08

Posts: 103

Website

Re: kworker consuming 100% cpu with empty stack

You'll get the same output for every kernel thread.

Well, not quite:

# cat /proc/<kworker_pid>/stack
[<ffffffff8108e5cf>] worker_thread+0xbf/0x4a0
[<ffffffff81093ff8>] kthread+0xd8/0xf0
[<ffffffff81591e8f>] ret_from_fork+0x3f/0x70
[<ffffffffffffffff>] 0xffffffffffffffff

Not to mention other threads that are actually doing something have some more depth to the stack.

Last edited by yuvadm (2016-02-20 09:37:56)

mich41

Member

Registered: 2012-06-22

Posts: 796

Re: kworker consuming 100% cpu with empty stack

Sorry, I tried on a different kernel. Anyway, perf record -g.