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From: John Ogness <john.ogness@linutronix.de>
To: xu.xin16@zte.com.cn, bigeasy@linutronix.de, rostedt@goodmis.org
Cc: zhang.yunkai@zte.com.cn, yang.yang29@zte.com.cn, liu.chun2@zte.com.cn,
 si.hao@zte.com.cn, linux-kernel@vger.kernel.org,
 linux-rt-users@vger.kernel.org, rostedt@goodmis.org, xu.xin16@zte.com.cn
Subject: Re: [PATCH  5.10-rt] printk: ignore that console preempted by
 irq/softirq
In-Reply-To: <20240523235537910_yxfGMbTcSOmMkcfuK2d8@zte.com.cn>
References: <20240523235537910_yxfGMbTcSOmMkcfuK2d8@zte.com.cn>
Date: Sun, 26 May 2024 19:52:04 +0206
Message-ID: <87ttiko49v.fsf@jogness.linutronix.de>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain

On 2024-05-23, <xu.xin16@zte.com.cn> wrote:
> From: xu xin <xu.xin16@zte.com.cn>
>
> When we're in the unpreemptible context on the same cpu with which the
> thread of console locates on, we should ignore this console for
> pr_flush, because it's a vain and always lead to timeout until the console
> thread get cpu resource.

Newer RT kernels do things quite differently. But for the 5.10-rt
implementation, I can see how the 1 second timeout could be annoying.

> Fixes: e65be5f4dc3ed("printk: Update John Ogness' printk series")
> Signed-off-by: xu xin <xu.xin16@zte.com.cn>
> Cc: Zhang Yunkai <zhang.yunkai@zte.com.cn>
> ---
> kernel/printk/printk.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/kernel/printk/printk.c b/kernel/printk/printk.c
> index 7f27cfee283e..faab85dd4439 100644
> --- a/kernel/printk/printk.c
> +++ b/kernel/printk/printk.c
> @@ -3735,6 +3735,14 @@ bool pr_flush(int timeout_ms, bool reset_on_progress)
> diff = 0;
>
> for_each_console(con) {
> + /*
> + * When we're in the unpreemptible context on the same cpu
> + * with which the thread of console locates on, we should
> + * ignore this console, because it's a vain.
> + */
> + if (!preemptible() && con->thread &&
> + task_cpu(con->thread) == smp_processor_id())
> + continue;
> if (!(con->flags & CON_ENABLED))
> continue;
> printk_seq = read_console_seq(con);

The code is OK, but you have lost the tab indenting. Perhaps these can
be added by the RT maintainer.

With the correct whitespace:

Reviewed-by: John Ogness <john.ogness@linutronix.de>