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    SubjectRe: [PATCH v2 1/4] drivers: hwspinlock: add generic framework
    * Ohad Ben-Cohen <ohad@wizery.com> [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


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