Re: [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
Thanks,
- Andy
> Reported-by: Alex Goins
> Signed-off-by: Sebastian Andrzej Siewior
> ---
> 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
Re: [PATCH RT] Align rt_mutex inlining with upstream behavior
On Fri, Feb 03, 2017 at 04:54:34PM +0100, Sebastian Andrzej Siewior wrote: > On 2017-01-30 09:35:34 [-0800], Andy Ritger wrote: > > The problem is that various static inline functions such as > > reservation_object_fini() indirectly call mutex_destroy. On DEBUG_MUTEX > > kernels, mutex_destroy is EXPORT_SYMBOL_GPL. > > 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. Thanks, - Andy
Re: [PATCH RT] Align rt_mutex inlining with upstream behavior
On Thu, Jan 26, 2017 at 06:01:09PM +0100, Sebastian Andrzej Siewior wrote: > On 2017-01-24 18:45:50 [-0800], Alex Goins wrote: > > mutex_destroy is no-op inline when DEBUG_MUTEX is not enabled. The RT Linux > > patches replace mutex_destroy() with rt_mutex_destroy(). This patch aligns > > rt_mutex_destroy() with mutex_destroy() by using the same no-op inline > > technique. > > > > Signed-off-by: Alex Goins > > Reviewed-by: Andy Ritger > > So what is the problem? Why are we doing this? There is still a check to > see if the lock is in use which is also done for the case where > DEBUG_MUTEX is disabled. The problem is that various static inline functions such as reservation_object_fini() indirectly call mutex_destroy. On DEBUG_MUTEX kernels, mutex_destroy is EXPORT_SYMBOL_GPL. In upstream, non-DEBUG_MUTEX kernels define mutex_destroy to a noop. This gives users the option of disabling DEBUG_MUTEX if they want to use non-GPL, reservation_object_fini()-using, kernel modules. In PREEMPTRT, non-DEBUG_MUTEX kernels export rt_mutex_destroy as EXPORT_SYMBOL_GPL, so users no longer have the work around of using DEBUG_MUTEX. This patch gives PREEMPTRT users the option of disabling DEBUG_MUTEX if they want to use such kernel modules, matching upstream behavior.
Re: include/linux/rtmutex.h: NOOP rt_mutex_destroy if !CONFIG_DEBUG_RT_MUTEXES
This seems consistent with the spirit of DEBUG_MUTEX in non-RT kernels,
so hopefully this is acceptable to the RT maintainers.
Reviewed-by: Andy Ritger
Thanks,
- Andy
On Tue, Oct 25, 2016 at 07:03:51PM -0700, Alex Goins wrote:
> mutex_destroy is no-op inline when DEBUG_MUTEX is not enabled. When
> mutex_destroy is indirectly used by non-GPL kernel modules that use inline
> functions such as reservation_object_fini(), users can use a kernel with
> DEBUG_MUTEX disabled to avoid a dependence on the GPL-only symbol
> mutex_destroy.
>
> The RT Linux patches replace mutex_destroy with rt_mutex_destroy.
> Currently, rt_mutex_destroy is GPL_ONLY irrespective of whether mutex
> debugging is enabled.
>
> This patch aligns rt_mutex_destroy with mutex_destroy by using the same
> no-op inline technique. This allows non-GPL modules to access the same
> functionality with RT Linux as with regular Linux.
>
> Signed-off-by: Alex Goins
> ---
> include/linux/rtmutex.h | 7 ++-
> kernel/locking/rtmutex.c | 5 ++---
> 2 files changed, 8 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/rtmutex.h b/include/linux/rtmutex.h
> index 1abba5c..741e844 100644
> --- a/include/linux/rtmutex.h
> +++ b/include/linux/rtmutex.h
> @@ -56,6 +56,12 @@ struct hrtimer_sleeper;
> #endif
>
> #ifdef CONFIG_DEBUG_RT_MUTEXES
> + extern void rt_mutex_destroy(struct rt_mutex *lock);
> +#else
> + static inline void rt_mutex_destroy(struct rt_mutex *lock) {}
> +#endif
> +
> +#ifdef CONFIG_DEBUG_RT_MUTEXES
> # define __DEBUG_RT_MUTEX_INITIALIZER(mutexname) \
> , .name = #mutexname, .file = __FILE__, .line = __LINE__
> # define rt_mutex_init(mutex)__rt_mutex_init(mutex,
> __func__)
> @@ -87,7 +93,6 @@ static inline int rt_mutex_is_locked(struct rt_mutex *lock)
> }
>
> extern void __rt_mutex_init(struct rt_mutex *lock, const char *name);
> -extern void rt_mutex_destroy(struct rt_mutex *lock);
>
> extern void rt_mutex_lock(struct rt_mutex *lock);
> extern int rt_mutex_lock_interruptible(struct rt_mutex *lock);
> diff --git a/kernel/locking/rtmutex.c b/kernel/locking/rtmutex.c
> index 1ec0f48..8d3a80e 100644
> --- a/kernel/locking/rtmutex.c
> +++ b/kernel/locking/rtmutex.c
> @@ -1513,6 +1513,7 @@ bool __sched rt_mutex_futex_unlock(struct rt_mutex
> *lock,
> return rt_mutex_slowunlock(lock, wqh);
> }
>
> +#ifdef CONFIG_DEBUG_RT_MUTEXES
> /**
> * rt_mutex_destroy - mark a mutex unusable
> * @lock: the mutex to be destroyed
> @@ -1524,12 +1525,10 @@ bool __sched rt_mutex_futex_unlock(struct rt_mutex
> *lock,
> void rt_mutex_destroy(struct rt_mutex *lock)
> {
> WARN_ON(rt_mutex_is_locked(lock));
> -#ifdef CONFIG_DEBUG_RT_MUTEXES
> lock->magic = NULL;
> -#endif
> }
> -
> EXPORT_SYMBOL_GPL(rt_mutex_destroy);
> +#endif
>
> /**
> * __rt_mutex_init - initialize the rt lock
