On 09/14/2015 09:57 AM, Peter Zijlstra wrote:
On Fri, Sep 11, 2015 at 02:37:37PM -0400, Waiman Long wrote:+#define queued_spin_trylock(l) pv_queued_spin_trylock_unfair(l) +static inline bool pv_queued_spin_trylock_unfair(struct qspinlock *lock) +{ + struct __qspinlock *l = (void *)lock; + + if (READ_ONCE(l->locked)) + return 0; + /* + * Wait a bit here to ensure that an actively spinning vCPU has a fair + * chance of getting the lock. + */ + cpu_relax(); + + return cmpxchg(&l->locked, 0, _Q_LOCKED_VAL) == 0; +} +static inline int pvstat_trylock_unfair(struct qspinlock *lock) +{ + int ret = pv_queued_spin_trylock_unfair(lock); + + if (ret) + pvstat_inc(pvstat_utrylock); + return ret; +} +#undef queued_spin_trylock +#define queued_spin_trylock(l) pvstat_trylock_unfair(l)These aren't actually ever used...
The pvstat_trylock_unfair() is within the CONFIG_QUEUED_LOCK_STAT block. It will only be activated when the config parameter is set. Otherwise, pv_queued_spin_trylock_unfair() will be used without any counting.
It is used provide count of how many unfair trylock has successfully got the lock.
Cheers, Longman -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
