Re: bad return value in __mutex_lock_check_stamp

[Nicholas Mc Guire <der.herr@hofr.at>]

On Sun, 15 Dec 2013, Sebastian Andrzej Siewior wrote:

> On 12/15/2013 03:40 PM, Nicholas Mc Guire wrote:
> > 
> > Bad return value in _mutex_lock_check_stamp - this problem only would show 
> > up with 3.12.1 rt4 applied but CONFIG_PREEMPT_RT_FULL not enabled 
> > currently it would be returning what ever vprintk_emit ended up with 
> > (atleast on x86), which probably is not the intended behavior. Added a
> > return 0; as in the case with CONFIG_PREEMPT_RT_FULL enabled.
> 
> Interesting. How do you trigger this? This BUG()-only function should
> get completely removed by gcc because
> - ctx argument should be always NULL
> - BUG() has unreachable() so gcc knows it does not return.
>
poped up with randconfig seed 0xBE96A834

Don't get it - why could gcc optimize it out ? it gets called
in the mutex slowpath (kernel/mutex.c) if CONFIG_PREEMPT_RT_FULL
is not set ?

Am I confusing some ifdefs ?

thx!
hofrat