From: Jim Nelson <james4765@verizon.net>
To: "Randy.Dunlap" <rddunlap@osdl.org>
Cc: Keith Owens <kaos@ocs.com.au>, Jim Nelson <james4765@cwazy.co.uk>,
Alan Cox <alan@lxorguk.ukuu.org.uk>,
Coywolf Qi Hunt <coywolf@gmail.com>,
Jesper Juhl <juhl-lkml@dif.dk>,
David Howells <dhowells@redhat.com>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: printk loglevel policy?
Date: Sun, 02 Jan 2005 23:44:03 -0500 [thread overview]
Message-ID: <41D8CD93.8000200@verizon.net> (raw)
In-Reply-To: <41D8C161.5000102@osdl.org>
Randy.Dunlap wrote:
> Keith Owens wrote:
>
>> On Sun, 02 Jan 2005 13:41:34 -0800, "Randy.Dunlap" <rddunlap@osdl.org>
>> wrote:
>>
>>> Jim Nelson wrote:
>>>
>>>> Or does printk() do some tracking that I didn't see as to where in
>>>> the kernel the strings are coming from?
>>>
>>>
>>> That kind of garbled output has been known to happen, but
>>> the <console_sem> is supposed to prevent that (along with
>>> zap_locks() in kernel/printk.c).
>>
>>
>>
>> Using multiple calls to printk to print a single line has always been
>> subject to the possibility of interleaving on SMP. We just live with
>> the risk. Printing a complete line in a single call to printk is
>> protected by various locks. Print a line in multiple calls is not
>> protected. If it bothers you that much, build up the line in a local
>> buffer then call printk once.
>
>
> True, I was thinking about the single line case, which I
> have seen garbled/mixed in the past (on SMP). Hopefully
> that one is fixed.
>
Okay, that answered my question. Is is frowned upon to use strncat/strcat in the
kernel? I have yet to see any use of them outside of the definition in
lib/string.c. It would seem to be faster (less potential contention for the
printk locks).
next prev parent reply other threads:[~2005-01-03 4:43 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-12-31 2:02 [patch] add loglevel to printk in fs/afs/cmservice.c Jesper Juhl
2004-12-31 2:20 ` printk loglevel policy? Coywolf Qi Hunt
2004-12-31 4:07 ` Jim Nelson
2004-12-31 4:34 ` Jesper Juhl
2005-01-02 14:36 ` Alan Cox
2005-01-02 19:01 ` Jim Nelson
2005-01-02 21:41 ` Randy.Dunlap
2005-01-03 3:17 ` Keith Owens
2005-01-03 3:52 ` Randy.Dunlap
2005-01-03 4:44 ` Jim Nelson [this message]
2005-01-04 10:46 ` David Howells
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