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SubjectRe: [debug patch] printk: Add a printk killswitch to robustify NMI watchdog messages

* Peter Zijlstra <peterz@infradead.org> wrote:

> On Wed, 2011-06-08 at 21:17 +0200, Ingo Molnar wrote:
> > Hm, the no-wakeup aspect seems rather useful.
> >
> > Could we perhaps remove console_sem and replace it with a mutex and
> > do something like this with a mutex and its ->wait_lock?
> >
> > We'd have two happy side effects:
> >
> > - we'd thus remove one of the last core kernel semaphore users
> > - we'd gain lockdep coverage for console locking as a bonus ...
>
> The mutex thing is more complex due to the mutex fast path, the
> advantage of the semaphore is its simple implementation that always
> takes the internal lock.
>
> I guess I can make it happen, but its a tad more tricky.

Hm, i thought it would be possible to only express it via the
slowpath: if mutex_trylock() succeeds then *all* execution goes into
the slowpath so we don't have to take all the fastpaths into account.

If that's notpossible then i think you and Linus are right that it's
not worth creating all the per arch fastpath special cases for
something like this.

The non-removal of the console_sem is sad though. Sniff.

Thanks,

Ingo


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