linux-kernel - Re: [PATCH] IB/mlx5:: pr_err() and mlx5_ib_dbg() strings should end with newlines

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Message-ID: <20170926155006.GD6816@mtr-leonro.local>
Date:   Tue, 26 Sep 2017 18:50:06 +0300
From:   Leon Romanovsky <leonro@...lanox.com>
To:     Joe Perches <joe@...ches.com>
Cc:     Arvind Yadav <arvind.yadav.cs@...il.com>, matanb@...lanox.com,
        dledford@...hat.com, sean.hefty@...el.com,
        hal.rosenstock@...il.com, linux-rdma@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] IB/mlx5:: pr_err() and mlx5_ib_dbg() strings should end
 with newlines

On Tue, Sep 26, 2017 at 08:05:37AM -0700, Joe Perches wrote:
> On Tue, 2017-09-26 at 11:38 +0300, Leon Romanovsky wrote:
> > On Tue, Sep 26, 2017 at 12:20:01PM +0530, Arvind Yadav wrote:
> > > pr_err() and mlx5_ib_dbg( messages should terminated with a new-line to
> > > avoid other messages being concatenated.
> []
> > Did you see it is happening?
> > It is not needed after 4bcc595ccd80 ("printk: reinstate KERN_CONT for printing continuation lines")
>
> Not completely true, and that commit message
> itself is incorrect about how KERN_CONT was
> ever required or not required.
>
> After that commit, the dmesg output will
> eventually be corrected with an appended newline
> for sine line format strings without them, but
> the printk subsystem has to wait for another
> printk to occur before inserting that newline.
>
> The commit message bit that says:
>
>     Things get much hairier when you have
>     multiple threads going on and user level
>     reading and writing logs too
>
> is correct.  That's the actual reason that
> the proposed newline additions are reasonable.
>

I asked that question after I tried locally various different options
with/without newline and didn't see any difference.

So how can I reproduce the different output before and after this change?

Thanks

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