Jan Kiszka wrote: > 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.
The number of knots in my brain is already increasing. Before this gets critical: Could you send me your rtnet.o (or .ko) privately? Without the patch applied. I need to have a look at the disassembly. BTW, SMP or UP? Further question: Did you find any messages in your kernel log after loosing packets? Something about dropped packets? TiA, Jan
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