* Ohad Ben-Cohen <ohad@xxxxxxxxxx> [101123 07:27]: > Add a common, platform-independent, hwspinlock framework. > > Hardware spinlock devices are needed, e.g., in order to access data > that is shared between remote processors, that otherwise have no > alternative mechanism to accomplish synchronization and mutual exclusion > operations. <snip> > + int hwspin_lock(struct hwspinlock *hwlock); > + - lock a previously assigned hwspinlock. If the hwspinlock is already > + taken, the function will busy loop waiting for it to be released. > + Note: if a faulty remote core never releases this lock, this function > + will deadlock. > + This function will fail only if hwlock is invalid. Otherwise, it will > + always succeed (or deadlock; see above) and it will never sleep. > + Upon a successful return from this function, preemption is disabled so > + the caller must not sleep, and is advised to release the hwspinlock as > + soon as possible, in order to minimize remote cores polling on the > + hardware interconnect. ... > + int hwspin_lock_timeout(struct hwspinlock *hwlock, unsigned long timeout); > + - lock a previously-assigned hwspinlock with a timeout limit (specified in > + jiffies). If the hwspinlock is already taken, the function will busy loop > + waiting for it to be released, but give up when the timeout meets jiffies. > + If timeout is 0, the function will never give up (therefore if a faulty > + remote core never releases the hwspinlock, it will deadlock). > + Upon a successful return from this function, preemption is disabled so > + the caller must not sleep, and is advised to release the hwspinlock as > + soon as possible, in order to minimize remote cores polling on the > + hardware interconnect. > + Returns 0 when successful and an appropriate error code otherwise (most > + notably -ETIMEDOUT if the hwspinlock is still busy after timeout meets > + jiffies). The function will never sleep. Do we even need the hwspin_lock variants, why can't we always use the hwspin_lock_timeout variants? To me the idea of looping waiting for some external system to release a lock is not a good idea.. Regards, Tony -- To unsubscribe from this list: send the line "unsubscribe linux-omap" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
