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Date: Thu, 1 Sep 2011 10:37:44 +0800
From: Yong Zhang <yong.zhang0@...il.com>
To: Shan Hai <haishan.bai@...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 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.
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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