On Sat, Sep 28, 2002 at 02:27:44PM -0400, Robert Love wrote:
> > NMI interrupt handler cannot block so it trylocks against a spinlock
> > instead. Buffer processing code needs to block against concurrent NMI
> > interrupts so takes the spinlock for them. All actual blocks on the
> > spinlock are beneath a down() on another semaphore, so a sleep whilst
> > holding the spinlock won't actually cause deadlock.
>
> If all accesses to the spinlock are taken under a semaphore, then the
> spinlock is not needed (i.e. the down'ed semaphore provides the same
> protection), or am I missing something?
>
> If this is not the case - e.g. there are other accesses to these locks -
> then you cannot sleep, no?
The other accessors are spin_trylock()ers, as I mentioned. They will not
block but they are not under the semaphore.
The spinlock cannot be a semaphore because NMI interrupts do not take to
kindly to up()
regards
john
-- "When your name is Winner, that's it. You don't need a nickname." - Loser Lane - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
This archive was generated by hypermail 2b29 : Mon Sep 30 2002 - 22:00:38 EST