On (03/02/16 14:38), Petr Mladek wrote:
[..]
> >
> > CONFIG_PREEMPT_NONE=y
> > # CONFIG_PREEMPT_VOLUNTARY is not set
> > # CONFIG_PREEMPT is not set
> > CONFIG_PREEMPT_COUNT=y
>
> preempt_disable() / preempt_enable() would do the job.
> The question is where to put it. If you are concerned about
> the delay, you might want to disable preemption around
> the whole locked area, so that it works reasonable also
> in the preemptive kernel.
another question is why cond_resched() is suddenly so expensive?
my guess is because of OOM, so we switch to tasks that potentially
do direct reclaims, etc. if so, then even offloaded printk will take
a significant amount of time to print the logs to the consoles; just
because it does cond_resched() after every call_console_drivers().
> I am looking forward to have the console printing offloaded
> into the workqueues. Then printk() will become consistently
> "fast" operation and will cause less surprises like this.
I'm all for it. I need this rework badly. If Jan is too busy at
the moment, which I surely can understand, then I'll be happy to
help ("pick up the patches". please, don't get me wrong).
-ss
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