Messages in this thread | | | Date | Tue, 11 Sep 2007 09:20:23 -0700 (PDT) | From | Matti Linnanvuori <> | Subject | Do not deprecate binary semaphore or do allow mutex in software interrupt contexts |
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Arjan van de Ven: > what do you do if the trylock fails?
Just do not read the status variable now but modify the timer to run later.
> to be honest, the scenario describe really smells of broken locking, in > fact it really sounds like it wants to use spinlocks instead
No, I don't think it is broken. Spinlocks can be used, but I don't see them being obviously better in all cases. If access takes a long time, it is better to sleep during it. And if you sleep, you might just end up creating a new mutex implementation with a spinlock.
Alan Cox: > For polling and timer based code its often simpler to do > > del_timer_sync(&my_timer); > FrobStuff > add_timer(&my_timer); > > especially if "FrobStuff" is likely to change when you next need to poll.
In the scenario I presented, the timer modifies itself to run later. Therefore, simply calling del_timer_sync is not enough but you have to set an atomic variable to prevent the timer from adding itself again. Again, you end up creating a new mutex implementation, which is not good.
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