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Date: Thu, 1 Jun 2006 16:00:45 -0700
From: Andrew Morton <akpm@osdl.org>
To: "Antonino A. Daplas" <adaplas@gmail.com>
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Subject: Re: OpenGL-based framebuffer concepts
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"Antonino A. Daplas" <adaplas@gmail.com> wrote:
>
> Console writes are done with the console semaphore held. printk will also
> just write to the log buffer and defer the actual console printing
> for later, by the next or current process that will grab the semaphore.

Always by the current process which holds console_sem.  Leaving the printing
for the next process would be unacceptably too late for printk.

If printk sees that someone holds console_sem, printk will leave the data
in the log buffer for the current holder of console_sem to print, prior to
that caller releasing console_sem.  logbuf_log is used in tricky ways
around console_sem to prevent races in this logic.