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

[Shan Hai <haishan.bai@xxxxxxxxx>]

On 09/01/2011 10:37 AM, Yong Zhang wrote:
> 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.

Got it.

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?

My fault, should replace the lock type too, thanks for the suggestion.

Best regards
Shan Hai

> 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
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
> > the body of a message to majordomo@xxxxxxxxxxxxxxx
> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> > Please read the FAQ at  http://www.tux.org/lkml/

--
To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html