Re: [Patch v5] rwsem: fix rwsem_is_locked() bugs

[Cong Wang]

Andrew Morton wrote:
> On Wed, 14 Oct 2009 05:52:22 -0400
> Amerigo Wang <amwang@xxxxxxxxxx> wrote:
>
> > --- a/include/linux/rwsem-spinlock.h
> > +++ b/include/linux/rwsem-spinlock.h
> > @@ -68,11 +68,9 @@ extern int __down_write_trylock(struct rw_semaphore *sem);
> >  extern void __up_read(struct rw_semaphore *sem);
> >  extern void __up_write(struct rw_semaphore *sem);
> >  extern void __downgrade_write(struct rw_semaphore *sem);
> > +extern int __rwsem_is_locked(struct rw_semaphore *sem);
> >  
> > -static inline int rwsem_is_locked(struct rw_semaphore *sem)
> > -{
> > -	return (sem->activity != 0);
> > -}
> > +#define rwsem_is_locked(sem) __rwsem_is_locked(sem)
> >  
> >  #endif /* __KERNEL__ */
> >  #endif /* _LINUX_RWSEM_SPINLOCK_H */
> > diff --git a/lib/rwsem-spinlock.c b/lib/rwsem-spinlock.c
> > index 9df3ca5..7014306 100644
> > --- a/lib/rwsem-spinlock.c
> > +++ b/lib/rwsem-spinlock.c
> > @@ -17,6 +17,19 @@ struct rwsem_waiter {
> >  #define RWSEM_WAITING_FOR_WRITE	0x00000002
> >  };
> >  
> > +int __rwsem_is_locked(struct rw_semaphore *sem)
> > +{
> > +	int ret = 1;
> > +	unsigned long flags;
> > +
> > +	if (spin_trylock_irqsave(&sem->wait_lock, flags)) {
> > +		ret = (sem->activity != 0);
> > +		spin_unlock_irqrestore(&sem->wait_lock, flags);
> > +	}
> > +	return ret;
> > +}
> > +EXPORT_SYMBOL(__rwsem_is_locked);
>
> Why the macro tricks?  Can we do


Yes, better.

Thanks for your patch!

> --- a/include/linux/rwsem-spinlock.h~rwsem-fix-rwsem_is_locked-bugs-fix
> +++ a/include/linux/rwsem-spinlock.h
> @@ -68,9 +68,7 @@ extern int __down_write_trylock(struct r
>  extern void __up_read(struct rw_semaphore *sem);
>  extern void __up_write(struct rw_semaphore *sem);
>  extern void __downgrade_write(struct rw_semaphore *sem);
> -extern int __rwsem_is_locked(struct rw_semaphore *sem);
> -
> -#define rwsem_is_locked(sem) __rwsem_is_locked(sem)
> +extern int rwsem_is_locked(struct rw_semaphore *sem);
>  
>  #endif /* __KERNEL__ */
>  #endif /* _LINUX_RWSEM_SPINLOCK_H */
> --- a/lib/rwsem-spinlock.c~rwsem-fix-rwsem_is_locked-bugs-fix
> +++ a/lib/rwsem-spinlock.c
> @@ -17,7 +17,7 @@ struct rwsem_waiter {
>  #define RWSEM_WAITING_FOR_WRITE	0x00000002
>  };
>  
> -int __rwsem_is_locked(struct rw_semaphore *sem)
> +int rwsem_is_locked(struct rw_semaphore *sem)
>  {
>  	int ret = 1;
>  	unsigned long flags;
> @@ -28,7 +28,7 @@ int __rwsem_is_locked(struct rw_semaphor
>  	}
>  	return ret;
>  }
> -EXPORT_SYMBOL(__rwsem_is_locked);
> +EXPORT_SYMBOL(rwsem_is_locked);
>  
>  /*
>   * initialise the semaphore
> _

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