M. Koehrer wrote: > Hi everybody, > > I have the assumption that one IRQ lock is missing in stackmgr_task(): > In my setup I have two realtime NICs in use with rtnet. > And for this setup, I think the assumption in the function stackmgr_task() > > /* we are the only reader => no locking required */ > skb = __rtskb_fifo_remove(&rx.fifo); > > is not valid, as the interrupt routine of the NIC could write to rx.fifo via > rtnetif_rx() while the stackmgr_task() > is about to read from rx.fifo (eg. triggered by the other NIC's IRQ). > Even with With one NIC it is not save when there many short messages arriving > very fast.
In theory it is safe. > > Thus, I think the line above has to be changed to > skb = rtskb_fifo_remove(&rx.fifo); > > to be really save! > > I actually had a problem with lost packages with two NICs enabled. I hope the > fix above helps to fix the issue. > At least, the first short test looks promising. Well, not good. That's why using lock-less algorithms is so much fun: it's fairly easy to shot yourself in the knee without even knowing it... I'm going to rethink this carefully again. For now your patch is likely the safest way to go, although it voids the whole optimisation idea. [Damn, I was sure this were ok.] Thanks, Jan
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