linux-kernel - Garbled printk output on 2.7.27

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Message-ID: <f22d86810910270024o4cd69265v61536afedc0e510b@mail.gmail.com>
Date:	Tue, 27 Oct 2009 00:24:43 -0700
From:	"Leonidas ." <leonidas137@...il.com>
To:	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Garbled printk output on 2.7.27 - No multi line printks

Hi,

I am trying a simple char driver and for debug purposes I have added
lot of printks
in my module. The module is rather heavily being used by my test app which does
hundreds of open/read/write calls. The driver just copies and prints
incoming/outgoing
buffers.

I see a lot of garbled output in /var/log/messages

E.g.

Oct 27 00:18:47 ubuntu-vm kernel: [ 4903.382917] returned buf  "Hello"
Oct 27 00:18:47 ubuntu-vm kernel: [ 4903.382925] returned buf "Hello"
Oct 27 00:18:47 ubuntu-vm kernel: [ 4903.383033] returned buf "Hello"
reeeeeeeeeexeeeeeeexteeeexeeeeeeeeeeeeeeeeeeeeeeeeeeeeexeeeeeeeeeeeeeeeeeexeeeeeeeeeexteexeeeeeeeeexeeeeeeeeeeeeeeeeeeeeeeexeeeeeeeeeeeexeeeeeeeeeeeexeeeeeeeeeeeeeeeeeeeeexeeeeeeeeeeeeeeeeeeexeeeeeeeeeexteeeeeeeeeeeeeeexeeeext
for 8902 Hello
Oct 27 00:18:47 ubuntu-vm kernel: [ d
Oct 27 00:18:47 ubuntu-vm kernel: dddddddd
Oct 27 00:18:47 ubuntu-vm kernel:
ddddddddn3eexeeeeeeeeeeeeeeeexeeeeeeeeeeeeexeeeeexteeeeeeexeeeeeeeeeeeeeeeeeeeeeeeeeeexeeeeeeeeeexeeeeeeeeeeexeeeeeeeeeeeeexeeeeeeeeeeeeeexeeeeeeeeeexeeeeexeeeeeeeeeeeeeeeeeeeeeeexeeeeeeeeeeeeeeeeeeeeexeeeeeeeeeexeeeeeeeeeeeeeeeeexeeeeeeeext
for 8903 Hello


My loglevel is KERN_INFO, my understanding was a multiline printk
might cause garbled output
on SMPs but a single line printk is always protected using a semaphore.

-Leo.
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