On 02/12/2015 08:30 PM, Peter Zijlstra wrote:
On Thu, Feb 12, 2015 at 05:17:27PM +0530, Raghavendra K T wrote:
[...]
Linus suggested that we should not do any writes to lock after unlock(),
and we can move slowpath clearing to fastpath lock.
So this patch implements the fix with:
1. Moving sl
On Thu, Feb 12, 2015 at 05:17:27PM +0530, Raghavendra K T wrote:
> Paravirt spinlock clears slowpath flag after doing unlock.
> As explained by Linus currently it does:
> prev = *lock;
> add_smp(&lock->tickets.head, TICKET_LOCK_INC);
>
> /* add_smp()
On 02/12/2015 07:32 PM, Oleg Nesterov wrote:
Damn, sorry for noise, forgot to mention...
On 02/12, Raghavendra K T wrote:
+static inline void __ticket_check_and_clear_slowpath(arch_spinlock_t *lock,
+ __ticket_t head)
+{
+ if (head &
On 02/12/2015 07:20 PM, Oleg Nesterov wrote:
On 02/12, Raghavendra K T wrote:
@@ -191,8 +189,7 @@ static inline void arch_spin_unlock_wait(arch_spinlock_t
*lock)
* We need to check "unlocked" in a loop, tmp.head == head
* can be false positive because of overf
On 02/12/2015 07:07 PM, Oleg Nesterov wrote:
On 02/12, Raghavendra K T wrote:
@@ -772,7 +773,8 @@ __visible void kvm_lock_spinning(struct arch_spinlock
*lock, __ticket_t want)
* check again make sure it didn't become free while
* we weren't looking.
*/
- if (AC
Damn, sorry for noise, forgot to mention...
On 02/12, Raghavendra K T wrote:
>
> +static inline void __ticket_check_and_clear_slowpath(arch_spinlock_t *lock,
> + __ticket_t head)
> +{
> + if (head & TICKET_SLOWPATH_FLAG) {
> + arc
On 02/12, Raghavendra K T wrote:
>
> @@ -191,8 +189,7 @@ static inline void arch_spin_unlock_wait(arch_spinlock_t
> *lock)
>* We need to check "unlocked" in a loop, tmp.head == head
>* can be false positive because of overflow.
>*/
> - if
On 02/12, Raghavendra K T wrote:
>
> @@ -772,7 +773,8 @@ __visible void kvm_lock_spinning(struct arch_spinlock
> *lock, __ticket_t want)
>* check again make sure it didn't become free while
>* we weren't looking.
>*/
> - if (ACCESS_ONCE(lock->tickets.head) == want) {
>
Paravirt spinlock clears slowpath flag after doing unlock.
As explained by Linus currently it does:
prev = *lock;
add_smp(&lock->tickets.head, TICKET_LOCK_INC);
/* add_smp() is a full mb() */
if (unlikely(lock->tickets.tail & TICKET_
