Re: [PATCH] kernel/hung_task: Add a whitelist and blacklist mechanism.

From: Tetsuo Handa
Date: Sat Apr 17 2021 - 10:46:14 EST

On 2021/04/17 23:13, zhouchuangao wrote:
> The main purpose of this patch is to add a whitelist and blacklist
> mechanism to the hung task thread.

We stopped using the term 'whitelist'/'blacklist' for new code in Linux kernel,
and what you are proposing is something like 'ignorelist'/'fatallist'.

I think that matching based on comm name is poor, for comm name is subjected to
impersonation by malicious user processes.

Moreover, speak of syzkaller testing, most of hang task reports are reaction to
somebody else consuming too much CPU resources (e.g. printk() flooding, too many
pending workqueue requests). Even if some process is in 'ignorelist', it is
possible that some problem that should be reported is already happening. Even if
some process is in 'fatallist', it is possible that the cause of hang is simply
somebody else is consuming too much CPU.

By the way, I wish that khungtaskd can report recent top CPU consumers, for it is
rare that the cause of hung is locking dependency problems / hardware problems.