[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Xen-devel] [PATCH v5 2/8] qspinlock, x86: Enable x86-64 to use queue spinlock
- To: Waiman Long <Waiman.Long@xxxxxx>
- From: Oleg Nesterov <oleg@xxxxxxxxxx>
- Date: Sun, 2 Mar 2014 15:10:58 +0100
- Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>, kvm@xxxxxxxxxxxxxxx, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, Andi Kleen <andi@xxxxxxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Michel Lespinasse <walken@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, linux-arch@xxxxxxxxxxxxxxx, Gleb Natapov <gleb@xxxxxxxxxx>, x86@xxxxxxxxxx, Ingo Molnar <mingo@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx>, Arnd Bergmann <arnd@xxxxxxxx>, Scott J Norton <scott.norton@xxxxxx>, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, Steven Rostedt <rostedt@xxxxxxxxxxx>, Chris Wright <chrisw@xxxxxxxxxxxx>, Alok Kataria <akataria@xxxxxxxxxx>, Aswin Chandramouleeswaran <aswin@xxxxxx>, Chegu Vinod <chegu_vinod@xxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, David Vrabel <david.vrabel@xxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Sun, 02 Mar 2014 14:26:08 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
On 02/26, Waiman Long wrote:
>
> +#define _ARCH_SUPPORTS_ATOMIC_8_16_BITS_OPS
> +
> +/*
> + * x86-64 specific queue spinlock union structure
> + */
> +union arch_qspinlock {
> + struct qspinlock slock;
> + u8 lock; /* Lock bit */
> +};
And this enables the optimized version of queue_spin_setlock().
But why does it check ACCESS_ONCE(qlock->lock) == 0 ? This is called
right after queue_get_lock_qcode() returns 0, this locked should be
likely unlocked.
Oleg.
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel
|
