Re: [Xen-devel] [PATCH] spinlock: improve spin_is_locked() for recursive locks

["Xu, Quan" <quan.xu@xxxxxxxxx>]

On March 24, 2016 7:31pm, <jbeulich@xxxxxxxx> wrote:
> Recursive locks know their current owner, and since we use the function solely
> to determine whether a particular lock is being held by the current CPU (which
> so far has been an imprecise check), make actually check the owner for
> recusrively acquired locks.
> 
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> --- a/xen/common/spinlock.c
> +++ b/xen/common/spinlock.c
> @@ -188,7 +188,9 @@ void _spin_unlock_irqrestore(spinlock_t
>  int _spin_is_locked(spinlock_t *lock)
>  {
>      check_lock(&lock->debug);
> -    return lock->tickets.head != lock->tickets.tail;
> +    return lock->recurse_cpu == SPINLOCK_NO_CPU
> +           ? lock->tickets.head != lock->tickets.tail
> +           : lock->recurse_cpu == smp_processor_id();
>  }
> 
>  int _spin_trylock(spinlock_t *lock)
> 
> 

Reviewed-by: Quan Xu <quan.xu@xxxxxxxxx>

Thanks for your enhancement. I am not aware of this case in my previous patch 
set.
Quan



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