linux-kernel - Re: [PATCH] lib/vsprintf: add %pT[C012] format specifier

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Message-Id: <201401062302.FJG51045.tFSOFJQLOOHFMV@I-love.SAKURA.ne.jp>
Date:	Mon, 6 Jan 2014 23:02:09 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	pavel@....cz
Cc:	keescook@...omium.org, joe@...ches.com, akpm@...ux-foundation.org,
	geert@...ux-m68k.org, jkosina@...e.cz, viro@...iv.linux.org.uk,
	davem@...emloft.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lib/vsprintf: add %pT[C012] format specifier

Pavel Machek wrote:
> > + * Please use this wrapper function which will be updated in the future to read
> > + * @tsk->comm in a consistent way.
> > + */
> > +static inline int commcmp(const struct task_struct *tsk, const char *comm)
> > +{
> > +	return strcmp(tsk->comm, comm);
> > +}
> 
> Is this useful to something? Printing command name is
> useful. Comparing it...?
>

(a) Using tsk->comm for reducing duplicated printk() messages.

    if (strcmp(p->comm, last_comm)) {
        printk("hello\n");
        strcpy(last_comm, p->comm);
    }

(b) Using tsk->pid for reducing duplicated printk() messages.

    if (p->pid != last_pid) {
        printk("hello\n");
        last_pid = p->pid;
    }

(c) Using printk_ratelimit() for reducing printk() flooding.

    printk_ratelimit("hello\n");

(d) Using plain printk().

    printk("hello\n");

(e) Other purposes. (e.g. drivers/target/iscsi/iscsi_target_tq.c )

    if (!strncmp(current->comm, ISCSI_RX_THREAD_NAME,
                 strlen(ISCSI_RX_THREAD_NAME)))
        thread_called = ISCSI_RX_THREAD;
    else if (!strncmp(current->comm, ISCSI_TX_THREAD_NAME,
                      strlen(ISCSI_TX_THREAD_NAME)))
        thread_called = ISCSI_TX_THREAD;

commcmp() and commcpy() are for wrappring (a).
Though (a) should consider changing to (b) or (c).

(e) should be rewritten not to depend on current->comm .
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