Re: [Xen-devel] [PATCH v1 6/9] spinlock: Introduce spin_lock_cb()

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Mar 24, 2017 at 01:05:01PM -0400, Boris Ostrovsky wrote:
> While waiting for a lock we may want to periodically run some
> code. We could use spin_trylock() but since it doesn't take lock
> ticket it may take a long time until the lock is taken.
> 
> Add spin_lock_cb() that allows us to execute a callback while waiting.
> Also add spin_lock_kick() that will wake up the waiters.
> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> ---
>  xen/common/spinlock.c      |   20 ++++++++++++++++++++
>  xen/include/xen/spinlock.h |    3 +++
>  2 files changed, 23 insertions(+), 0 deletions(-)
> 
> diff --git a/xen/common/spinlock.c b/xen/common/spinlock.c
> index 2a06406..d1de3ca 100644
> --- a/xen/common/spinlock.c
> +++ b/xen/common/spinlock.c
> @@ -129,6 +129,26 @@ static always_inline u16 observe_head(spinlock_tickets_t 
> *t)
>      return read_atomic(&t->head);
>  }
>  
> +void _spin_lock_cb(spinlock_t *lock, void (*cb)(void *), void *data)
> +{
> +    spinlock_tickets_t tickets = SPINLOCK_TICKET_INC;
> +    LOCK_PROFILE_VAR;
> +
> +    check_lock(&lock->debug);
> +    tickets.head_tail = arch_fetch_and_add(&lock->tickets.head_tail,
> +                                           tickets.head_tail);
> +    while ( tickets.tail != observe_head(&lock->tickets) )
> +    {
> +        LOCK_PROFILE_BLOCK;
> +        if ( cb )
> +            cb(data);
> +        arch_lock_relax();
> +    }
> +    LOCK_PROFILE_GOT;
> +    preempt_disable();
> +    arch_lock_acquire_barrier();
> +}
> +
>  void _spin_lock(spinlock_t *lock)

You should be able to use _spin_lock_cb to implement _spin_lock, right?

Wei.

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