linux-kernel - Re: [PATCH v2 1/2] printk: Fix panic caused by passing log_buf

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Message-ID: <20180925122300.qq5w4skwmxbzi6sy@pathway.suse.cz>
Date:   Tue, 25 Sep 2018 14:23:00 +0200
From:   Petr Mladek <pmladek@...e.com>
To:     Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        He Zhe <zhe.he@...driver.com>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] printk: Fix panic caused by passing log_buf_len
 to command line

On Tue 2018-09-25 21:01:35, Sergey Senozhatsky wrote:
> On (09/21/18 09:37), Petr Mladek wrote:
> > 
> > I would personally keep the size as unsigned int. IMHO, a support
> > for a log buffer bigger than 4GB is not worth the complexity.
> > 
> 
> ftrace dumps are bothering me.
> 
> Steven Rostedt wrote [0]:
> >
> > Especially when I have a machine with 240 CPUs. But it also has a ton of
> > RAM, I could easily do log_buf_len=32G
> >
> 
> The systems are getting bigger, so log_buf_len=UINT_MAX+ might become
> a norm at some point.

Thanks for pointing this out. Well, it seems that the change would
require a new syscall to pass the buffer size as long. We need to
be sure that people would use this in the real life.

This thread suggested this change to avoid a checkpatch warning.
The 32GB was mentioned as an example one year ego. This is not enough
for a new syscall from my point of view.

Best Regards,
Petr