On Tue, Jun 09, 2015 at 05:18:18PM +0530, Vineet Gupta wrote:
Please try and provide at least _some_ Changelog body.
<snip all atomic ops that return values>
> diff --git a/arch/arc/include/asm/spinlock.h b/arch/arc/include/asm/spinlock.h
> index b6a8c2dfbe6e..8af8eaad4999 100644
> --- a/arch/arc/include/asm/spinlock.h
> +++ b/arch/arc/include/asm/spinlock.h
> @@ -22,24 +22,32 @@ static inline void arch_spin_lock(arch_spinlock_t *lock)
> {
> unsigned int tmp = __ARCH_SPIN_LOCK_LOCKED__;
>
> + smp_mb();
> +
> __asm__ __volatile__(
> "1: ex %0, [%1] \n"
> " breq %0, %2, 1b \n"
> : "+&r" (tmp)
> : "r"(&(lock->slock)), "ir"(__ARCH_SPIN_LOCK_LOCKED__)
> : "memory");
> +
> + smp_mb();
> }
>
> static inline int arch_spin_trylock(arch_spinlock_t *lock)
> {
> unsigned int tmp = __ARCH_SPIN_LOCK_LOCKED__;
>
> + smp_mb();
> +
> __asm__ __volatile__(
> "1: ex %0, [%1] \n"
> : "+r" (tmp)
> : "r"(&(lock->slock))
> : "memory");
>
> + smp_mb();
> +
> return (tmp == __ARCH_SPIN_LOCK_UNLOCKED__);
> }
>
Both these are only required to provide an ACQUIRE barrier, if all you
have is smp_mb(), the second is sufficient.
Also note that a failed trylock is not required to provide _any_ barrier
at all.
> @@ -47,6 +55,8 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
> {
> unsigned int tmp = __ARCH_SPIN_LOCK_UNLOCKED__;
>
> + smp_mb();
> +
> __asm__ __volatile__(
> " ex %0, [%1] \n"
> : "+r" (tmp)
This requires a RELEASE barrier, again, if all you have is smp_mb(),
this is indeed correct.
Describing some of this would make for a fine Changelog body :-)
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