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

From: Shan Hai
Date: Wed Aug 31 2011 - 23:02:49 EST

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

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