From: Remy Bohmer
Date: Mon Aug 15 2011 - 16:44:43 EST


> Besides of the cpu load i also found out that with rt11 i can again wake up
> usermode from a IRQF_NO_THREAD waiting on a waitqueue. So the steps outlined
> in this mail do not
> seem to be neccessary anymore? Or does this create an error and than some high
> load?

Try running with CONFIG_DEBUG_SPINLOCK_SLEEP and you would probably
see some errors...

If you have CONFIG_PREEMPT_RT_FULL set, then the __wake_up function of
the waitqueue runs into a spinlock. This spinlock will be converted to
a mutex since it is a regular spinlock, not a raw_spinlock. A
mutex-lock might sleep. Calling sleeping functions from hard-irq
context is illegal.

Kind regards,

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