Re: [PATCH V2] x86 spinlock: Fix memory corruption on completing completions

2015-02-09 Thread Raghavendra K T
Ccing Davidlohr, (sorry that I got confused with similar address in cc list). On 02/09/2015 08:44 PM, Oleg Nesterov wrote: On 02/09, Raghavendra K T wrote: +static inline void __ticket_check_and_clear_slowpath(arch_spinlock_t *lock) +{ + arch_spinlock_t old, new; + __ticket_t diff;

Re: [PATCH V2] x86 spinlock: Fix memory corruption on completing completions

2015-02-09 Thread Oleg Nesterov
On 02/09, Raghavendra K T wrote: > > +static inline void __ticket_check_and_clear_slowpath(arch_spinlock_t *lock) > +{ > + arch_spinlock_t old, new; > + __ticket_t diff; > + > + old.tickets = READ_ONCE(lock->tickets); > + diff = (old.tickets.tail & ~TICKET_SLOWPATH_FLAG) - old.ticke

[PATCH V2] x86 spinlock: Fix memory corruption on completing completions

2015-02-09 Thread Raghavendra K T
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_