[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <Zs3nRK4ikgzMx7JU@pathway.suse.cz>
Date: Tue, 27 Aug 2024 16:48:36 +0200
From: Petr Mladek <pmladek@...e.com>
To: John Ogness <john.ogness@...utronix.de>
Cc: Sergey Senozhatsky <senozhatsky@...omium.org>,
Steven Rostedt <rostedt@...dmis.org>,
Thomas Gleixner <tglx@...utronix.de>, linux-kernel@...r.kernel.org,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Subject: Re: [PATCH printk v4 06/17] printk: nbcon: Introduce printer kthreads
On Tue 2024-08-27 06:49:22, John Ogness wrote:
> From: Thomas Gleixner <tglx@...utronix.de>
>
> Provide the main implementation for running a printer kthread
> per nbcon console that is takeover/handover aware. This
> includes:
>
> - new mandatory write_thread() callback
> - kthread creation
> - kthread main printing loop
> - kthread wakeup mechanism
> - kthread shutdown
>
> --- a/kernel/printk/nbcon.c
> +++ b/kernel/printk/nbcon.c
> @@ -1036,6 +1042,219 @@ static bool nbcon_emit_next_record(struct nbcon_write_context *wctxt, bool use_a
[...]
> +/*
> + * nbcon_kthread_stop - Stop a console printer thread
> + * @con: Console to operate on
> + */
> +void nbcon_kthread_stop(struct console *con)
> +{
> + lockdep_assert_console_list_lock_held();
> +
> + if (!con->kthread)
> + return;
> +
> + kthread_stop(con->kthread);
> + con->kthread = NULL;
> +}
> +
> +/**
> + * nbcon_kthread_create - Create a console printer thread
> + * @con: Console to operate on
> + *
> + * Return: True if the kthread was started or already exists.
> + * Otherwise false and @con must not be registered.
> + *
> + * If @con was already registered, it must be unregistered before
> + * the global state variable @printk_kthreads_running can be set.
This paragraph is quite confusing without more context. I would
either remove it completely or write something like:
<proposal>
* This function is called when nbcon consoles are supposed to be flushed
* using the kthread. The messages printed with NBCON_PRIO_NORMAL are not
* longer flushed by the legacy loop. This is why the failure is considered
* fatal leading to the console unregistration.
</proposal>
> + */
> +bool nbcon_kthread_create(struct console *con)
> +{
> + struct task_struct *kt;
> +
> + lockdep_assert_console_list_lock_held();
> +
> + if (con->kthread)
> + return true;
> +
> + kt = kthread_run(nbcon_kthread_func, con, "pr/%s%d", con->name, con->index);
> + if (WARN_ON(IS_ERR(kt))) {
> + con_printk(KERN_ERR, con, "failed to start printing thread\n");
> + return false;
> + }
> +
> + con->kthread = kt;
> +
> + return true;
> +}
> +
> /* Track the nbcon emergency nesting per CPU. */
> static DEFINE_PER_CPU(unsigned int, nbcon_pcpu_emergency_nesting);
> static unsigned int early_nbcon_pcpu_emergency_nesting __initdata;
> @@ -1419,6 +1644,13 @@ bool nbcon_alloc(struct console *con)
> con_printk(KERN_ERR, con, "failed to allocate printing buffer\n");
> return false;
> }
> +
> + if (printk_kthreads_running) {
> + if (!nbcon_kthread_create(con)) {
> + kfree(con->pbufs);
It probably is not much important but I would rather do here:
con->pbufs = NULL;
> + return false;
> + }
> + }
> }
>
> return true;
Otherwise, it looks good. With the two proposed changes:
Reviewed-by: Petr Mladek <pmladek@...e.com>
Best Regards,
Petr
Powered by blists - more mailing lists