Manfred Spraul wrote:
>
> > - Major revamp of printk(). The approach taken in printk() is to try
> > to acquire the (new) console_sem. If we succeed, the output is
> > placed into the log buffer and is printed to the consoles. If we fail
> > to acquire the semaphore we just buffer the output in the log buffer
> > and the current holder of the console_sem will do the printing for us
> > prior to releasing console_sem.
>
> Is down_trylock reliable under load?
I'm not aware of any problems. It's only really used in one
place at present - when networking interrupt context wants to
acquire a socket's semaphore. Oh. That seems to have disappeared.
I've tested it pretty hard on SMP with zillions of printk()s from
interrupt context in parallel with `cat lots_of_stuff'.
> I remember 2 or 3 bug reports than disappeared after down_trylock was
> removed.
> The last one was this week.
>
> http://www.mail-archive.com/linux-kernel@vger.kernel.org/msg31919.html
That was different. The parport code was leaving the semaphore in
a downed state when it shouldn't have.
But you're right - it's not well-proven code. I'll go stare
angrily at it for a while. Of course, there are about ten
different implementations...
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