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Date: Tue, 20 Feb 2001 14:05:15 -0800
From: Robert Read <rread@datarithm.net>
To: linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Re: kernel/printk.c: increasing the buffer size to capture devfsd debug messages.
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In-Reply-To: <3A92D930.6F11B505@cypress.com>; from ted@cypress.com on Tue, Feb 20, 2001 at 02:53:04PM -0600
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On Tue, Feb 20, 2001 at 02:53:04PM -0600, Thomas Dodd wrote:
> Robert Read wrote:
> 
> Why not just make the config option in Kbytes.
> and do:
> 
> #define LOG_BUF_LEN (CONFIG_PRINTK_BUF_LEN * 1024)
> 

This is good idea, but I believe LOG_BUF_LEN needs to be a power of
2.  A bitmask is used in several places to wrap around the end of the
ring buffer.  For example

#define LOG_BUF_MASK	 (LOG_BUF_LEN-1)

printk() {
  ....
  log_buf[(log_start+log_size) & LOG_BUF_MASK] = *p;
}


I think LOG_BUF_LEN could be defined to round up (or down) at compile
time, but my post-lunch-sleepy brain can't think of the trick to do
it.

robert
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