Re: [PATCH 0/5] kthread: increase the size of kthread's comm

[Al Viro]

On Wed, Sep 29, 2021 at 11:50:31AM +0000, Yafang Shao wrote:

> That motivates me to do this improvement.
> 
> This patch increases the size of ktread's comm from 16 to 24, which is
> the same with workqueue's. After this change, the name of kthread can be
> fully displayed in /proc/[pid]/comm, for example,
>     
>     rcu_tasks_kthread
>     rcu_tasks_rude_kthread
>     rcu_tasks_trace_kthread
>     ecryptfs-kthread
>     vfio-irqfd-cleanup
>     ext4-rsv-conversion
>     jbd2/nvme0n1p2-8
>     ...
>     
> Because there're only a few of kthreads, so it won't increase too much
> memory consumption.

That's a bloody massive overkill.  If you care about /proc/*/comm, you
might want to take a look at the function that generates its contents:

void proc_task_name(struct seq_file *m, struct task_struct *p, bool escape)
{
        char tcomm[64];

        if (p->flags & PF_WQ_WORKER)
                wq_worker_comm(tcomm, sizeof(tcomm), p);
        else   
                __get_task_comm(tcomm, sizeof(tcomm), p);

        if (escape)
                seq_escape_str(m, tcomm, ESCAPE_SPACE | ESCAPE_SPECIAL, "\n\\");
        else   
                seq_printf(m, "%.64s", tcomm);
}

Hint: it's not always p->comm verbatim...