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Date: Thu, 01 Sep 2011 11:02:48 +0800
From: Shan Hai <haishan.bai@...il.com>
To: Yong Zhang <yong.zhang0@...il.com>
CC: akpm@...ux-foundation.org, eric.dumazet@...il.com,
vapier@...too.org, asharma@...com, linux-kernel@...r.kernel.org,
linux-rt-users@...r.kernel.org,
Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 1/1 -rt] lib:atomic64 using raw_spin_lock_irq[save|resotre]
for atomicity
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@...il.com>
> 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
>>
>> --
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