linux-kernel - Re: [Patch v5] rwsem: fix rwsem_is

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Date:	Fri, 16 Oct 2009 09:28:41 +0800
From:	Cong Wang <amwang@...hat.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	linux-kernel@...r.kernel.org, Ben Woodard <bwoodard@...l.gov>,
	David Howells <dhowells@...hat.com>,
	Brian Behlendorf <behlendorf1@...l.gov>
Subject: Re: [Patch v5] rwsem: fix rwsem_is_locked() bugs

Andrew Morton wrote:
> On Wed, 14 Oct 2009 05:52:22 -0400
> Amerigo Wang <amwang@...hat.com> 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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