rtmutex: Warn if trylock is called from hard/softirq context
rtmutex: Warn if trylock is called from hard/softirq context

rt_mutex_trylock() must be called from thread context. It can be
called from atomic regions (preemption or interrupts disabled), but
not from hard/softirq/nmi context. Add a warning to alert abusers.

The reasons for this are:

    1) There is a potential deadlock in the slowpath

    2) Another cpu which blocks on the rtmutex will boost the task
       which allegedly locked the rtmutex, but that cannot work
       because the hard/softirq context borrows the task context.

Signed-off-by: Thomas Gleixner <00e4cf8f46a57000a44449bf9dd8cbbcc209fd2a@linutronix.de>
Cc: Peter Zijlstra <3fddac958924aef220f202ca567388ddab3f14a8@infradead.org>
Cc: Sebastian Siewior <265264fed90bdf8e813a354375ec16f47ebdb1c5@linutronix.de>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs