Re: [PATCH 1/1 -rt] lib:atomic64 usingraw_spin_lock_irq[save|resotre] for atomicity

[Yong Zhang]

On Thu, Sep 01, 2011 at 09:28:00AM +0800, Shan Hai wrote:
> The spin_lock_irq[save|restore] could break the atomicity of the
> atomic64_* operations in the PREEMPT-RT configuration, because
> the spin_lock_irq[save|restore] themselves are preemptable in the
> PREEMPT-RT, using raw variant of the spin lock could provide the
> atomicity that atomic64_* need.
> 
> Signed-off-by: Shan Hai <haishan.bai@xxxxxxxxx>

I think you could show your panic info also in the header.

And this should be routed to tglx(Cc'ing), and also to
linux-rt-users.

comments below:

> ---
>  lib/atomic64.c |   40 ++++++++++++++++++++--------------------
>  1 files changed, 20 insertions(+), 20 deletions(-)
> 
> diff --git a/lib/atomic64.c b/lib/atomic64.c
> index e12ae0d..26f524a 100644
> --- a/lib/atomic64.c
> +++ b/lib/atomic64.c
> @@ -48,9 +48,9 @@ long long atomic64_read(const atomic64_t *v)
>  	spinlock_t *lock = lock_addr(v);
>  	long long val;
>  
> -	spin_lock_irqsave(lock, flags);
> +	raw_spin_lock_irqsave(lock, flags);
>  	val = v->counter;
> -	spin_unlock_irqrestore(lock, flags);
> +	raw_spin_unlock_irqrestore(lock, flags);

I think this is indeed a problem;
but I don't see you touch the declaration and initialising of the lock,
why?

Thanks,
Yong

>  	return val;
>  }
>  EXPORT_SYMBOL(atomic64_read);
> @@ -60,9 +60,9 @@ void atomic64_set(atomic64_t *v, long long i)
>  	unsigned long flags;
>  	spinlock_t *lock = lock_addr(v);
>  
> -	spin_lock_irqsave(lock, flags);
> +	raw_spin_lock_irqsave(lock, flags);
>  	v->counter = i;
> -	spin_unlock_irqrestore(lock, flags);
> +	raw_spin_unlock_irqrestore(lock, flags);
>  }
>  EXPORT_SYMBOL(atomic64_set);
>  
> @@ -71,9 +71,9 @@ void atomic64_add(long long a, atomic64_t *v)
>  	unsigned long flags;
>  	spinlock_t *lock = lock_addr(v);
>  
> -	spin_lock_irqsave(lock, flags);
> +	raw_spin_lock_irqsave(lock, flags);
>  	v->counter += a;
> -	spin_unlock_irqrestore(lock, flags);
> +	raw_spin_unlock_irqrestore(lock, flags);
>  }
>  EXPORT_SYMBOL(atomic64_add);
>  
> @@ -83,9 +83,9 @@ long long atomic64_add_return(long long a, atomic64_t *v)
>  	spinlock_t *lock = lock_addr(v);
>  	long long val;
>  
> -	spin_lock_irqsave(lock, flags);
> +	raw_spin_lock_irqsave(lock, flags);
>  	val = v->counter += a;
> -	spin_unlock_irqrestore(lock, flags);
> +	raw_spin_unlock_irqrestore(lock, flags);
>  	return val;
>  }
>  EXPORT_SYMBOL(atomic64_add_return);
> @@ -95,9 +95,9 @@ void atomic64_sub(long long a, atomic64_t *v)
>  	unsigned long flags;
>  	spinlock_t *lock = lock_addr(v);
>  
> -	spin_lock_irqsave(lock, flags);
> +	raw_spin_lock_irqsave(lock, flags);
>  	v->counter -= a;
> -	spin_unlock_irqrestore(lock, flags);
> +	raw_spin_unlock_irqrestore(lock, flags);
>  }
>  EXPORT_SYMBOL(atomic64_sub);
>  
> @@ -107,9 +107,9 @@ long long atomic64_sub_return(long long a, atomic64_t *v)
>  	spinlock_t *lock = lock_addr(v);
>  	long long val;
>  
> -	spin_lock_irqsave(lock, flags);
> +	raw_spin_lock_irqsave(lock, flags);
>  	val = v->counter -= a;
> -	spin_unlock_irqrestore(lock, flags);
> +	raw_spin_unlock_irqrestore(lock, flags);
>  	return val;
>  }
>  EXPORT_SYMBOL(atomic64_sub_return);
> @@ -120,11 +120,11 @@ long long atomic64_dec_if_positive(atomic64_t *v)
>  	spinlock_t *lock = lock_addr(v);
>  	long long val;
>  
> -	spin_lock_irqsave(lock, flags);
> +	raw_spin_lock_irqsave(lock, flags);
>  	val = v->counter - 1;
>  	if (val >= 0)
>  		v->counter = val;
> -	spin_unlock_irqrestore(lock, flags);
> +	raw_spin_unlock_irqrestore(lock, flags);
>  	return val;
>  }
>  EXPORT_SYMBOL(atomic64_dec_if_positive);
> @@ -135,11 +135,11 @@ long long atomic64_cmpxchg(atomic64_t *v, long long o, long long n)
>  	spinlock_t *lock = lock_addr(v);
>  	long long val;
>  
> -	spin_lock_irqsave(lock, flags);
> +	raw_spin_lock_irqsave(lock, flags);
>  	val = v->counter;
>  	if (val == o)
>  		v->counter = n;
> -	spin_unlock_irqrestore(lock, flags);
> +	raw_spin_unlock_irqrestore(lock, flags);
>  	return val;
>  }
>  EXPORT_SYMBOL(atomic64_cmpxchg);
> @@ -150,10 +150,10 @@ long long atomic64_xchg(atomic64_t *v, long long new)
>  	spinlock_t *lock = lock_addr(v);
>  	long long val;
>  
> -	spin_lock_irqsave(lock, flags);
> +	raw_spin_lock_irqsave(lock, flags);
>  	val = v->counter;
>  	v->counter = new;
> -	spin_unlock_irqrestore(lock, flags);
> +	raw_spin_unlock_irqrestore(lock, flags);
>  	return val;
>  }
>  EXPORT_SYMBOL(atomic64_xchg);
> @@ -164,12 +164,12 @@ int atomic64_add_unless(atomic64_t *v, long long a, long long u)
>  	spinlock_t *lock = lock_addr(v);
>  	int ret = 0;
>  
> -	spin_lock_irqsave(lock, flags);
> +	raw_spin_lock_irqsave(lock, flags);
>  	if (v->counter != u) {
>  		v->counter += a;
>  		ret = 1;
>  	}
> -	spin_unlock_irqrestore(lock, flags);
> +	raw_spin_unlock_irqrestore(lock, flags);
>  	return ret;
>  }
>  EXPORT_SYMBOL(atomic64_add_unless);
> -- 
> 1.7.4.1
> 
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