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SubjectRe: [PATCH RT] Align rt_mutex inlining with upstream behavior
On Fri, Feb 10, 2017 at 06:50:50PM +0100, Sebastian Andrzej Siewior wrote:
> On 2017-02-03 08:49:24 [-0800], Andy Ritger wrote:
> > > So your problem is simply that your non-GPL module can't link anymore
> > > with -RT. Would it help you if I simply replace the export for
> > > mutex_destroy with EXPORT_SYMBOL and leave it the function as is?
> >
> > Yes, definitely.
>
> So this is what I intend to add to the RT patch and I hope Ingo won't
> object:
>
> Alex Goins reported that mutex_destroy() on RT will force a GPL only symbol
> which won't link and therefore fail on a non-GPL kernel module.
> This does not happen on !RT and is a regression on RT which we would like to
> avoid.
> I try here the easy thing and to not use rt_mutex_destroy() if
> CONFIG_DEBUG_MUTEXES is not enabled. This will still break for the DEBUG
> configs so instead of adding a wrapper around rt_mutex_destroy() (which we have
> for rt_mutex_lock() for instance) I am simply dropping the GPL part from the
> export.

Is the

WARN_ON(rt_mutex_is_locked(lock));

in rt_mutex_destroy() valuable in non-CONFIG_DEBUG_MUTEXES kernels,
such that it would be better to always call it, and not noop away mutex_destroy()
non-CONFIG_DEBUG_MUTEXES kernels? I thought that was your objection to
Alex's original patch.

But, with or without the noop-mutex_destroy diff hunk,

Reviewed-by: Andy Ritger <aritger@nvidia.com>

Thanks,
- Andy

> Reported-by: Alex Goins <agoins@nvidia.com>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
> include/linux/mutex_rt.h | 5 +++++
> kernel/locking/rtmutex.c | 3 +--
> 2 files changed, 6 insertions(+), 2 deletions(-)
>
> --- a/include/linux/mutex_rt.h
> +++ b/include/linux/mutex_rt.h
> @@ -43,7 +43,12 @@ extern void __lockfunc _mutex_unlock(str
> #define mutex_lock_killable(l) _mutex_lock_killable(l)
> #define mutex_trylock(l) _mutex_trylock(l)
> #define mutex_unlock(l) _mutex_unlock(l)
> +
> +#ifdef CONFIG_DEBUG_MUTEXES
> #define mutex_destroy(l) rt_mutex_destroy(&(l)->lock)
> +#else
> +static inline void mutex_destroy(struct mutex *lock) {}
> +#endif
>
> #ifdef CONFIG_DEBUG_LOCK_ALLOC
> # define mutex_lock_nested(l, s) _mutex_lock_nested(l, s)
> --- a/kernel/locking/rtmutex.c
> +++ b/kernel/locking/rtmutex.c
> @@ -2027,8 +2027,7 @@ void rt_mutex_destroy(struct rt_mutex *l
> lock->magic = NULL;
> #endif
> }
> -
> -EXPORT_SYMBOL_GPL(rt_mutex_destroy);
> +EXPORT_SYMBOL(rt_mutex_destroy);
>
> /**
> * __rt_mutex_init - initialize the rt lock
>
> Sebastian

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